Follow-up from "Show correct error message for Create and Update mutations on Snippet"

The following discussion from !33111 (merged) should be addressed:

• @tomquirk started a discussion: (+1 comment)

  issue (non-blocking): Not related to your MR but I feel like we can improve the error messages here (especially the GraphQL ones) - for example, from the screenshots in the MR description, "Can't update snippet: Repository error updating snippet - " seems unnecessarily repetitive (but, I understand the complexities in handling varying server-generated errors 😅 ).

  If there isn't an issue for this, WDYT about creating one?