Fix pagination headers for repository commits api endpoint

What does this MR do?

Adds pagination headers in the project repository commits api endpoint response.

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

The add_pagination_headers method in pagination helper module adds the project_id as a parameter in the pagination links. Though unnecessary does not break the produced pagination links.

Why was this MR needed?

In order to follow pagination specs as described in api docs.

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?

#20207 (closed)

Closes #13605 (closed)