Bump RuboCop to 0.67.2

Performance cops will be extracted from RuboCop to RuboCop Performance
when next RuboCop 0.68 will be released.
rubocop/rubocop#5977

RuboCop 0.67 is its transition period.

Since rails/rails repository uses Performance cops, This PR added
rubocop-performance gem to Gemfile.

And this PR fixes some offenses using the following auto-correct.

```console
% bundle exec rubocop -a

Offenses:

activerecord/test/cases/connection_adapters/connection_handlers_multi_db_test.rb:212:26:
C: [Corrected] Layout/SpaceAroundOperators: Operator =
> should be surrounded by a single space.
              "primary"  => { adapter: "sqlite3", database: "db/primary.sqlite3" }
                         ^^
activerecord/test/cases/connection_adapters/connection_handlers_multi_db_test.rb:239:26:
C: [Corrected] Layout/SpaceAroundOperators: Operator => should be
surrounded by a single space.
              "primary"  => { adapter: "sqlite3", database: "db/primary.sqlite3" }
                         ^^
actionview/test/template/resolver_shared_tests.rb:1:1: C: [Corrected]
Style/FrozenStringLiteralComment: Missing magic comment #
frozen_string_literal: true.
module ResolverSharedTests
^
actionview/test/template/resolver_shared_tests.rb:10:33: C: [Corrected]
Layout/SpaceAroundEqualsInParameterDefault: Surrounding space missing in
default value assignment.
  def with_file(filename, source="File at #{filename}")
                                ^
actionview/test/template/resolver_shared_tests.rb:106:5: C: [Corrected]
Rails/RefuteMethods: Prefer assert_not_same over refute_same.
    refute_same a, b
    ^^^^^^^^^^^

2760 files inspected, 5 offenses detected, 5 offenses corrected
```

.codeclimate.yml

@@ -25,6 +25,6 @@ checks:
 plugins:
   rubocop:
     enabled: true
-    channel: rubocop-0-66
+    channel: rubocop-0-67
 
 exclude_patterns: []

.rubocop.yml

@@ -1,3 +1,5 @@
+require: rubocop-performance
+
 AllCops:
   TargetRubyVersion: 2.5
   # RuboCop has a bunch of cops enabled by default. This setting tells RuboCop

Gemfile

@@ -29,6 +29,7 @@ gem "uglifier", ">= 1.3.0", require: false
 gem "json", ">= 2.0.0"
 
 gem "rubocop", ">= 0.47", require: false
+gem "rubocop-performance", require: false
 
 group :doc do
   gem "sdoc", "~> 1.0"

Gemfile.lock

@@ -411,14 +411,16 @@ GEM
       resque (~> 1.26)
       rufus-scheduler (~> 3.2)
     retriable (3.1.2)
-    rubocop (0.66.0)
+    rubocop (0.67.2)
       jaro_winkler (~> 1.5.1)
       parallel (~> 1.10)
       parser (>= 2.5, != 2.5.1.1)
       psych (>= 3.1.0)
       rainbow (>= 2.2.2, < 4.0)
       ruby-progressbar (~> 1.7)
       unicode-display_width (>= 1.4.0, < 1.6)
+    rubocop-performance (1.1.0)
+      rubocop (>= 0.67.0)
     ruby-progressbar (1.10.0)
     ruby-vips (2.0.13)
       ffi (~> 1.9)
@@ -581,6 +583,7 @@ DEPENDENCIES
   resque
   resque-scheduler
   rubocop (>= 0.47)
+  rubocop-performance
   sass-rails
   sdoc (~> 1.0)
   selenium-webdriver (>= 3.5.0, < 3.13.0)

actionview/test/template/resolver_shared_tests.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ResolverSharedTests
   attr_reader :tmpdir
 
@@ -7,7 +9,7 @@ def run(*args)
     end
   end
 
-  def with_file(filename, source="File at #{filename}")
+  def with_file(filename, source = "File at #{filename}")
     path = File.join(tmpdir, filename)
     FileUtils.mkdir_p(File.dirname(path))
     File.write(path, source)
@@ -103,7 +105,7 @@ def test_different_templates_when_cache_disabled
     c = context.find("hello_world", "test", false, [], {})
 
     # disable_cache should give us a new object
-    refute_same a, b
+    assert_not_same a, b
 
     # but it should not clear the cache
     assert_same a, c

activerecord/test/cases/connection_adapters/connection_handlers_multi_db_test.rb

@@ -209,7 +209,7 @@ def test_switching_connections_with_database_symbol_uses_default_role
           config = {
             "default_env" => {
               "animals" => { adapter: "sqlite3", database: "db/animals.sqlite3" },
-              "primary"  => { adapter: "sqlite3", database: "db/primary.sqlite3" }
+              "primary" => { adapter: "sqlite3", database: "db/primary.sqlite3" }
             }
           }
           @prev_configs, ActiveRecord::Base.configurations = ActiveRecord::Base.configurations, config
@@ -236,7 +236,7 @@ def test_switching_connections_with_database_hash_uses_passed_role_and_database
           config = {
             "default_env" => {
               "animals" => { adapter: "sqlite3", database: "db/animals.sqlite3" },
-              "primary"  => { adapter: "sqlite3", database: "db/primary.sqlite3" }
+              "primary" => { adapter: "sqlite3", database: "db/primary.sqlite3" }
             }
           }
           @prev_configs, ActiveRecord::Base.configurations = ActiveRecord::Base.configurations, config