Fix an obsolete option configuration values are duplicated when gener…

…ating `.rubocop_todo.yml`

Create two files with the following code:
```ruby
def fooBar; end
```

Set the following in .rubocop.yml:
```yml
Style/MethodName:
  IgnoredPatterns:
    - pattern1
    - pattern2
```

Run `rubocop --auto-gen-config`
Then duplicate configuration values are enumerated in `.rubocop_todo.yml` as follows:
```yml
# Offense count: 2
# Configuration parameters: EnforcedStyle, AllowedPatterns, IgnoredPatterns.
# SupportedStyles: snake_case, camelCase
# AllowedPatterns: pattern1, pattern2, pattern1, pattern2, pattern1, pattern2, pattern1, pattern2, pattern1, pattern2, pattern1, pattern2, pattern1, pattern2, pattern1, pattern2, pattern1, pattern2, pattern1, pattern2, pattern1, pattern2, pattern1, pattern2, pattern1, pattern2, pattern1, pattern2, pattern1, pattern2, pattern1, pattern2, pattern1, pattern2
Naming/MethodName:
  Exclude:
    - 'test1.rb'
    - 'test2.rb'
```

changelog/fix_fix_an_obsolete_option_configuration.md

@@ -0,0 +1 @@
+* [#10875](https://github.com/rubocop/rubocop/pull/10875): Fix an obsolete option configuration values are duplicated when generating `.rubocop_todo.yml`. ([@ydah][])

lib/rubocop/formatter/disabled_config_formatter.rb

@@ -161,7 +161,7 @@ def output_cop_param_comments(output_buffer, params, default_cfg)
           next unless value.is_a?(Array)
           next if value.empty?
 
-          output_buffer.puts "# #{param}: #{value.join(', ')}"
+          output_buffer.puts "# #{param}: #{value.uniq.join(', ')}"
         end
       end
 

spec/rubocop/cli/auto_gen_config_spec.rb

@@ -951,6 +951,33 @@ def a; end
       YAML
     end
 
+    context 'when configurable parameter is an obsolete parameter' do
+      it 'displayed as a new parameter setting value without duplication' do
+        create_file('.rubocop.yml', <<~YAML)
+          AllCops:
+            NewCops: enable
+          Naming/MethodName:
+            # `IgnoredPatterns` is obsolete. `AllowedPatterns` is newly used.
+            IgnoredPatterns:
+              - change
+              - not_change
+        YAML
+        create_file('example1.rb', ['# frozen_string_literal: true', '', 'def fooBar; end'])
+        create_file('example2.rb', ['# frozen_string_literal: true', '', 'def fooBar; end'])
+
+        expect(cli.run(['--auto-gen-config'])).to eq(0)
+        File.readlines('.rubocop_todo.yml')
+        expect(File.readlines('.rubocop_todo.yml')[9..].join)
+          .to eq(<<~YAML)
+            # Configuration parameters: AllowedPatterns, IgnoredPatterns.
+            # SupportedStyles: snake_case, camelCase
+            # AllowedPatterns: change, not_change
+            Naming/MethodName:
+              EnforcedStyle: camelCase
+          YAML
+      end
+    end
+
     it 'does not generate configuration for the Syntax cop' do
       create_file('example1.rb', <<~RUBY)
         # frozen_string_literal: true