Merge branch '508617-remove-feature-flag' into 'master'

Remove `fix_graphql_csrf` feature flag

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/178035



Merged-by: Andrew Evans <aevans@gitlab.com>
Approved-by: Ian Baum <ibaum@gitlab.com>
Approved-by: Ethan Urie <eurie@gitlab.com>
Approved-by: Andrew Evans <aevans@gitlab.com>
Reviewed-by: Heinrich Lee Yu <heinrich@gitlab.com>
Co-authored-by: Heinrich Lee Yu <heinrich@gitlab.com>