Merge branch '395809_update_epics_api_for_grape_update' into 'master'

Update Epics API for Grape 1.7 compatibility

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/121694



Merged-by: James Fargher <proglottis@gmail.com>
Approved-by: Nicolas Dular <ndular@gitlab.com>
Approved-by: James Fargher <proglottis@gmail.com>
Reviewed-by: Nicolas Dular <ndular@gitlab.com>
Co-authored-by: Vasilii Iakliushin <viakliushin@gitlab.com>