Add new InternalAffairs/RedundantContextConfigParameter cop

Follow up of rubocop/rubocop-rails#638 (comment).

This PR adds new `InternalAffairs/RedundantContextConfigParameter` cop
that checks for redundant `:config` parameter in the `context` arguments.

```ruby
# bad
context 'foo', :config do
end

# good
context 'foo' do
end
```

lib/rubocop/cop/internal_affairs.rb

@@ -9,6 +9,7 @@
 require_relative 'internal_affairs/node_matcher_directive'
 require_relative 'internal_affairs/node_type_predicate'
 require_relative 'internal_affairs/offense_location_keyword'
+require_relative 'internal_affairs/redundant_context_config_parameter'
 require_relative 'internal_affairs/redundant_described_class_as_subject'
 require_relative 'internal_affairs/redundant_let_rubocop_config_new'
 require_relative 'internal_affairs/redundant_location_argument'

lib/rubocop/cop/internal_affairs/redundant_context_config_parameter.rb

@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module InternalAffairs
+      # Checks for redundant `:config` parameter in the `context` arguments.
+      #
+      # @example
+      #
+      #   # bad
+      #   context 'foo', :config do
+      #   end
+      #
+      #   # good
+      #   context 'foo' do
+      #   end
+      #
+      class RedundantContextConfigParameter < Base
+        include RangeHelp
+        extend AutoCorrector
+
+        MSG = 'Remove the redundant `:config` parameter.'
+        RESTRICT_ON_SEND = %i[context].freeze
+
+        def on_send(node)
+          arguments = node.arguments
+          config_node = arguments.detect { |argument| argument.source == ':config' }
+          return unless config_node
+
+          add_offense(config_node) do |corrector|
+            dup_arguments = arguments.dup
+            dup_arguments.delete(config_node)
+
+            corrector.replace(offense_range(arguments), dup_arguments.map(&:source).join(', '))
+          end
+        end
+
+        private
+
+        def offense_range(arguments)
+          range_between(arguments.first.source_range.begin_pos, arguments.last.source_range.end_pos)
+        end
+      end
+    end
+  end
+end

spec/rubocop/cop/internal_affairs/redundant_context_config_parameter_spec.rb

@@ -0,0 +1,50 @@
+# frozen_string_literal: true
+
+RSpec.describe RuboCop::Cop::InternalAffairs::RedundantContextConfigParameter, :config do
+  it 'registers an offense when using `:config` parameter' do
+    expect_offense(<<~RUBY)
+      context 'foo', :config do
+                     ^^^^^^^ Remove the redundant `:config` parameter.
+      end
+    RUBY
+
+    expect_correction(<<~RUBY)
+      context 'foo' do
+      end
+    RUBY
+  end
+
+  it 'registers an offense when using `:config` parameter with other parameters' do
+    expect_offense(<<~RUBY)
+      context 'foo', :ruby30, :rails70, :config do
+                                        ^^^^^^^ Remove the redundant `:config` parameter.
+      end
+    RUBY
+
+    expect_correction(<<~RUBY)
+      context 'foo', :ruby30, :rails70 do
+      end
+    RUBY
+  end
+
+  it 'does not register an offense when not using `:config`' do
+    expect_no_offenses(<<~RUBY)
+      context 'foo' do
+      end
+    RUBY
+  end
+
+  it 'does not register an offense when using `:ruby30` only' do
+    expect_no_offenses(<<~RUBY)
+      context 'foo', :ruby30 do
+      end
+    RUBY
+  end
+
+  it 'does not register an offense when using `:config` in other than `context`' do
+    expect_no_offenses(<<~RUBY)
+      shared_context 'foo', :config do
+      end
+    RUBY
+  end
+end

spec/rubocop/cop/style/ascii_comments_spec.rb

@@ -19,7 +19,7 @@
     expect_no_offenses('# AZaz1@$%~,;*_`|')
   end
 
-  context 'when certain non-ascii chars are allowed', :config do
+  context 'when certain non-ascii chars are allowed' do
     let(:cop_config) { { 'AllowedChars' => ['∂'] } }
 
     it 'accepts comment with allowed non-ascii chars' do