Make Lint/DeprecatedConstants aware of Net::HTTPServerException

This PR makes `Lint/DeprecatedConstants` aware of `Net::HTTPServerException`.

The following warning was introduced since Ruby 2.6.

```console
% ruby -rnet/http -vwe 'p Net::HTTPServerException'
ruby 2.6.8p205 (2021-07-07 revision 67951) [x86_64-darwin19]
-e:1: warning: constant Net::HTTPServerException is deprecated
Net::HTTPServerException
```

And `HTTPClientException` (alias) is used as an alternative to `HTTPServerException`.

The following is the quote from Ruby 2.6.0 release news.

> Add `Net::HTTPClientException` to deprecate `Net::HTTPServerException`,
> whose name is misleading. [Bug #14688]

https://github.com/ruby/ruby/blob/master/doc/NEWS-2.6.0

```console
% ruby -rnet/http -vwe 'p Net::HTTPClientException'
ruby 2.6.8p205 (2021-07-07 revision 67951) [x86_64-darwin19]
Net::HTTPServerException
```

`HTTPClientException` does not yet exist in Ruby 2.5, so the following error occurs.

```console
% ruby -rnet/http -vwe 'p Net::HTTPClientException'
ruby 2.5.9p229 (2021-04-05 revision 67939) [x86_64-darwin19]
Traceback (most recent call last):
-e:1:in `<main>': uninitialized constant
Net::HTTPClientException (NameError)
Did you mean?  Net::HTTPServerException
```

To prevent such errors, the cop's behavior is changed to detect only `DeprecatedVersion` or higher.

changelog/change_make_deprecated_constants_aware_of_net_http_server_exception.md

@@ -0,0 +1 @@
+* [#10209](https://github.com/rubocop/rubocop/pull/10209): Make `Lint/DeprecatedConstants` aware of `Net::HTTPServerException`. ([@koic][])

config/default.yml

@@ -1568,6 +1568,7 @@ Lint/DeprecatedConstants:
   Description: 'Checks for deprecated constants.'
   Enabled: pending
   VersionAdded: '1.8'
+  VersionChanged: '<<next>>'
   # You can configure deprecated constants.
   # If there is an alternative method, you can set alternative value as `Alternative`.
   # And you can set the deprecated version as `DeprecatedVersion`.
@@ -1588,6 +1589,9 @@ Lint/DeprecatedConstants:
     'FALSE':
       Alternative: 'false'
       DeprecatedVersion: '2.4'
+    'Net::HTTPServerException':
+      Alternative: 'Net::HTTPClientException'
+      DeprecatedVersion: '2.6'
     'Random::DEFAULT':
       Alternative: 'Random.new'
       DeprecatedVersion: '3.0'

lib/rubocop/cop/lint/deprecated_constants.rb

@@ -42,11 +42,12 @@ def on_const(node)
           #        Maybe further investigation of RuboCop AST will lead to an essential solution.
           return unless node.loc
 
-          constant = node.absolute? ? constant_name(node, node.short_name.to_s) : node.source
+          constant = node.absolute? ? constant_name(node, node.short_name) : node.source
           return unless (deprecated_constant = deprecated_constants[constant])
 
           alternative = deprecated_constant['Alternative']
           version = deprecated_constant['DeprecatedVersion']
+          return if target_ruby_version < version.to_f
 
           add_offense(node, message: message(alternative, node.source, version)) do |corrector|
             corrector.replace(node, alternative)
@@ -56,7 +57,7 @@ def on_const(node)
         private
 
         def constant_name(node, nested_constant_name)
-          return nested_constant_name unless node.namespace.const_type?
+          return nested_constant_name.to_s unless node.namespace.const_type?
 
           constant_name(node.namespace, "#{node.namespace.short_name}::#{nested_constant_name}")
         end

spec/rubocop/cop/lint/deprecated_constants_spec.rb

@@ -7,6 +7,9 @@
         'NIL' => { 'Alternative' => 'nil', 'DeprecatedVersion' => '2.4' },
         'TRUE' => { 'Alternative' => 'true', 'DeprecatedVersion' => '2.4' },
         'FALSE' => { 'Alternative' => 'false', 'DeprecatedVersion' => '2.4' },
+        'Net::HTTPServerException' => {
+          'Alternative' => 'Net::HTTPClientException', 'DeprecatedVersion' => '2.6'
+        },
         'Random::DEFAULT' => { 'Alternative' => 'Random.new', 'DeprecatedVersion' => '3.0' },
         'Triple::Nested::Constant' => { 'Alternative' => 'Value', 'DeprecatedVersion' => '2.4' },
         'Have::No::Alternative' => { 'DeprecatedVersion' => '2.4' },
@@ -48,15 +51,57 @@
     RUBY
   end
 
-  it 'registers and corrects an offense when using `Random::DEFAULT`' do
-    expect_offense(<<~RUBY)
-      Random::DEFAULT
-      ^^^^^^^^^^^^^^^ Use `Random.new` instead of `Random::DEFAULT`, deprecated since Ruby 3.0.
-    RUBY
+  context 'Ruby <= 2.5', :ruby25 do
+    it 'does not register an offense when using `Net::HTTPServerException`' do
+      expect_no_offenses(<<~RUBY)
+        Net::HTTPServerException
+      RUBY
+    end
+  end
 
-    expect_correction(<<~RUBY)
-      Random.new
-    RUBY
+  context 'Ruby >= 2.6', :ruby26 do
+    it 'registers and corrects an offense when using `Net::HTTPServerException`' do
+      expect_offense(<<~RUBY)
+        Net::HTTPServerException
+        ^^^^^^^^^^^^^^^^^^^^^^^^ Use `Net::HTTPClientException` instead of `Net::HTTPServerException`, deprecated since Ruby 2.6.
+      RUBY
+
+      expect_correction(<<~RUBY)
+        Net::HTTPClientException
+      RUBY
+    end
+  end
+
+  context 'Ruby <= 2.7', :ruby27 do
+    it 'does not register an offense when using `Random::DEFAULT`' do
+      expect_no_offenses(<<~RUBY)
+        Random::DEFAULT
+      RUBY
+    end
+  end
+
+  context 'Ruby >= 3.0', :ruby30 do
+    it 'registers and corrects an offense when using `Random::DEFAULT`' do
+      expect_offense(<<~RUBY)
+        Random::DEFAULT
+        ^^^^^^^^^^^^^^^ Use `Random.new` instead of `Random::DEFAULT`, deprecated since Ruby 3.0.
+      RUBY
+
+      expect_correction(<<~RUBY)
+        Random.new
+      RUBY
+    end
+
+    it 'registers and corrects an offense when using `::Random::DEFAULT`' do
+      expect_offense(<<~RUBY)
+        ::Random::DEFAULT
+        ^^^^^^^^^^^^^^^^^ Use `Random.new` instead of `::Random::DEFAULT`, deprecated since Ruby 3.0.
+      RUBY
+
+      expect_correction(<<~RUBY)
+        Random.new
+      RUBY
+    end
   end
 
   it 'registers and corrects an offense when using `::NIL`' do
@@ -92,17 +137,6 @@
     RUBY
   end
 
-  it 'registers and corrects an offense when using `::Random::DEFAULT`' do
-    expect_offense(<<~RUBY)
-      ::Random::DEFAULT
-      ^^^^^^^^^^^^^^^^^ Use `Random.new` instead of `::Random::DEFAULT`, deprecated since Ruby 3.0.
-    RUBY
-
-    expect_correction(<<~RUBY)
-      Random.new
-    RUBY
-  end
-
   it 'registers and corrects an offense when using `::Triple::Nested::Constant`' do
     expect_offense(<<~RUBY)
       ::Triple::Nested::Constant