Delete award emoji when deleting a user

What does this MR do?

Fix the problem where a user's award emoji aren't deleted when the user is deleted.

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

The corresponding SELECT for the migration runs in 0.3s on staging, but I can't test the delete there or on production easily. It should be reasonably quick.

Why was this MR needed?

There was a typo in an association 😱

What are the relevant issue numbers?

Closes #19693 (closed).

Screenshots (if relevant)

Nope.

Does this MR meet the acceptance criteria?

• CHANGELOG entry added
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the style guides
• Branch has no merge conflicts with master (if you do - rebase it please)
• Squashed related commits together