Remove redundant class_name and foreign_key overrides

What does this MR do?

Remove redundant overrides in ActiveModel association declarations.

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

It is my very first MR.

Does this deserve a changelog entry?

Why was this MR needed?

To fix #23509 (closed)

Screenshots (if relevant)

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 merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #23509 (closed)