Merge branch '429270-discrepancy-with-api-runner-creation-registration-terminology' into 'master'

Update titles for API to create instance and user runners

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/138188



Merged-by: Lorena Ciutacu <lciutacu@gitlab.com>
Approved-by: Lorena Ciutacu <lciutacu@gitlab.com>
Co-authored-by: fneill <fneill@gitlab.com>