Remove EE-specific exception in .prettierignore

What does this MR do?

There was an EE-specific file listed directly in .prettierignore that will cause conflicts with CE. Since this is a very specific exception, I think it makes more sense to just use // prettier-ignore within the file itself and harmonize the EE/CE versions of .prettierignore.

What are the relevant issue numbers?

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• EE specific content should be in the top level /ee folder
• For a paid feature, have we considered GitLab.com plans, how it works for groups, and is there a design for promoting it to users who aren't on the correct plan?