Merge branch '177799-cleanup-fk-mrdf-project-id' into 'master'

Cleanup migrations adding merge_request_diff_files.project FK

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/184277



Merged-by: Adam Hegyi <ahegyi@gitlab.com>
Approved-by: Adam Hegyi <ahegyi@gitlab.com>
Reviewed-by: Alper Akgun <aakgun@gitlab.com>
Co-authored-by: Alper Akgun <aakgun@gitlab.com>
Co-authored-by: Gonzalo Servat <gservat@gitlab.com>
Co-authored-by: Dylan Griffith <dyl.griffith@gmail.com>