Fix remaining offenses for cop `Cop/StaticTranslationDefinition` related to diff_viewer

The following discussion from !100168 (merged) should be addressed:

• @splattael started a discussion:

  See https://gitlab.com/gitlab-org/gitlab/-/blob/0ff93efa9e72f85ed72112e186ec79dbe0face7d/app/models/diff_viewer/image.rb#L12

  It's a good idea to fix this a follow-up 👍 because it requires more work and more 👀 from domain experts.