Fix cross-project label references

What does this MR do?

It fixes cross-project label references if the same label exists in the same project or group.

Are there points in the code the reviewer needs to double check?

Make sure that update query doesn't accidentally update other label links.

Why was this MR needed?

Because some group labels were incorrectly updated when transferring projects in a group - #45539 (closed)

TODO

• bump schema version
• add more tests

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Conform by the code review guidelines
  • Has been reviewed by a UX Designer
  • Has been reviewed by a Frontend maintainer
  • Has been reviewed by a Backend maintainer
  • Has been reviewed by a Database specialist
• Conform by the merge request performance guides
• Conform by the style guides
• If you have multiple commits, please combine them into a few logically organized commits by squashing them
• Internationalization required/considered
• End-to-end tests pass (package-and-qa manual pipeline job)

What are the relevant issue numbers?

Closes #45539 (closed)