Add breaking change notice for Runner API stale value

data/deprecations/runner_api_new_stale_status_breaking_change.yml

+- name: "API: `stale` status returned instead of `offline` or `not_connected`"
+  announcement_milestone: "14.6" # The milestone when this feature was first announced as deprecated.
+  announcement_date: "2021-12-22"
+  removal_milestone: "15.0" # the milestone when this feature is planned to be removed
+  body: | # Do not modify this line, instead modify the lines below.
+    A breaking change will occur for the Runner [API](https://docs.gitlab.com/ee/api/runners.html#runners-api) endpoints in 15.0.
+
+    Instead of the GitLab Runner API endpoints returning `offline` and `not_connected` for runners that have not contacted the GitLab instance in the past three months, the API endpoints will return the `stale` value, which was introduced in 14.6.
+  stage: Verify
+  tiers: [Core, Premium, Ultimate]
+  issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/347303
+  documentation_url: https://docs.gitlab.com/ee/api/runners.html#runners-api

doc/update/deprecations.md

@@ -66,6 +66,14 @@ Announced: 2021-11-22
 
 ## 15.0
 
+### API: `stale` status returned instead of `offline` or `not_connected`
+
+A breaking change will occur for the Runner [API](https://docs.gitlab.com/ee/api/runners.html#runners-api) endpoints in 15.0.
+
+Instead of the GitLab Runner API endpoints returning `offline` and `not_connected` for runners that have not contacted the GitLab instance in the past three months, the API endpoints will return the `stale` value, which was introduced in 14.6.
+
+Announced: 2021-12-22
+
 ### Audit events for repository push events
 
 Audit events for [repository events](https://docs.gitlab.com/ee/administration/audit_events.html#repository-push) are now deprecated and will be removed in GitLab 15.0.