Merge branch 'docs-resource-group-api-tier' into 'master'

Add tier badge to Resource group API doc

See merge request gitlab-org/gitlab!76142

doc/api/resource_groups.md

@@ -2,10 +2,9 @@
 stage: Release
 group: Release
 info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments
-type: concepts, howto
 ---
 
-# Resource Groups API
+# Resource group API **(FREE)**
 
 You can read more about [controling the job concurrency with resource groups](../ci/resource_groups/index.md).