Fix an incorrect auto-correct for Style/ClassMethodsDefinitions

This PR fixes the following incorrect auto-correct for `Style/ClassMethodsDefinitions`
when defining class methods with `class << self` and there is no blank line between
method definition and attribute accessor.

```console
% cat example.rb
class A
  class << self
    def three
    end
    attr_reader :two
  end
end
```

```console
% bundle exec rubocop --only Style/ClassMethodsDefinitions -a
(snip)

Inspecting 1 file
C

Offenses:

example.rb:2:3: C: [Corrected] Style/ClassMethodsDefinitions: Do not
define public methods within class << self.
class << self ...
^^^^^^^^^^^^^

1 file inspected, 1 offense detected, 1 offense corrected
```

## Before

The syntax is broken as follows.

```console
% cat example.rb
class A
  class << self    attr_reader :two
  end

  def self.three
  end
end

% ruby -c example.rb
example.rb:2: syntax error, unexpected local variable or method,
expecting ';' or '\n'
class << self    attr_reader :two
example.rb:7: syntax error, unexpected `end', expecting end-of-input
```

## After

Safe auto-correction is done.

```console
% cat example.rb
class A
  class << self
  attr_reader :two
  end

  def self.three
  end
end
```

NOTE: This change may leave unwanted whitespace, which can be resolved with
`Layout/EmptyLinesAroundClassBody`. On the other hand, cannot auto-correction
for syntax error, so this PR fixes the syntax error first priority.

changelog/fix_an_incorrect_autocorrect_for_class_methods_definitions.md

@@ -0,0 +1 @@
+* [#9424](https://github.com/rubocop-hq/rubocop/pull/9424): Fix an incorrect auto-correct for `Style/ClassMethodsDefinitions` when defining class methods with `class << self` and there is no blank line between method definition and attribute accessor. ([@koic][])

lib/rubocop/cop/mixin/comments_help.rb

@@ -9,7 +9,6 @@ module CommentsHelp
       def source_range_with_comment(node)
         begin_pos = begin_pos_with_comment(node)
         end_pos = end_position_for(node)
-        end_pos += 1 if node.def_type?
 
         Parser::Source::Range.new(buffer, begin_pos, end_pos)
       end

spec/rubocop/cop/style/class_methods_definitions_spec.rb

@@ -19,6 +19,32 @@ def three
         end
       RUBY
 
+      expect_correction(<<~RUBY)
+        class A
+          class << self
+            attr_reader :two
+
+          end
+
+          def self.three
+          end
+        end
+      RUBY
+    end
+
+    it 'registers an offense and corrects when defining class methods with `class << self` and ' \
+       'there is no blank line between method definition and attribute accessor' do
+      expect_offense(<<~RUBY)
+        class A
+          class << self
+          ^^^^^^^^^^^^^ Do not define public methods within class << self.
+            def three
+            end
+            attr_reader :two
+          end
+        end
+      RUBY
+
       expect_correction(<<~RUBY)
         class A
           class << self
@@ -50,6 +76,7 @@ def two
         class A
           class << self
             attr_reader :one
+
           end
 
           # Multiline
@@ -139,6 +166,7 @@ class A
           class << self
             def self.one
             end
+
           end
 
           def self.two