Merge branch 'alvin-master-patch-42644' into 'master'

Update billable members

See merge request gitlab-org/gitlab!55577

doc/api/members.md

@@ -237,6 +237,8 @@ Example response:
 
 Gets a list of group members that count as billable. The list includes members in the subgroup or subproject.
 
+This API endpoint works on top-level groups only. It does not work on subgroups.
+
 NOTE:
 Unlike other API endpoints, billable members is updated once per day at 12:00 UTC.