Merge branch 'ph/423046/diffFileCommentsAPI' into 'master'

Fixes bug where position_type file wasn't accepted in API

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/130404



Merged-by: Bojan Marjanovic <bmarjanovic@gitlab.com>
Approved-by: Bojan Marjanovic <bmarjanovic@gitlab.com>
Co-authored-by: Phil Hughes <me@iamphill.com>