Suppress InternalAffairs/ProcessedSourceBufferName's offense

This commit suppresses the following `InternalAffairs/ProcessedSourceBufferName`'s offense:

```console
$ bundle exec rake
(snip)

lib/rubocop/cop/rails/deprecated_active_model_errors_methods.rb:163:28: C: [Correctable] InternalAffairs/ProcessedSourceBufferName: Use file_path instead.
processed_source.buffer.name.include?('/models/')
                 ^^^^^^^^^^^

279 files inspected, 1 offense detected, 1 offense autocorrectable
```

lib/rubocop/cop/rails/deprecated_active_model_errors_methods.rb

@@ -160,7 +160,7 @@ def receiver_matcher(node)
         end
 
         def model_file?
-          processed_source.buffer.name.include?('/models/')
+          processed_source.file_path.include?('/models/')
         end
       end
     end