Merge branch '431713-move-custom-roles-strings-out-of-constants-file' into 'master'

Move custom member roles strings out of constants file

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/140005



Merged-by: David Pisek <dpisek@gitlab.com>
Approved-by: David Pisek <dpisek@gitlab.com>
Co-authored-by: Daniel Tian <dtian@gitlab.com>