Document the removal of JenkinsDeprecatedService

doc/api/services.md

@@ -1303,6 +1303,9 @@ GET /projects/:id/services/jenkins
 
 A continuous integration and build server
 
+NOTE: **Note:**
+This service was [removed in v13.0](https://gitlab.com/gitlab-org/gitlab/-/issues/1600)
+
 ### Create/Edit Jenkins CI (Deprecated) service
 
 Set Jenkins CI (Deprecated) service for a project.

doc/integration/jenkins_deprecated.md

@@ -6,6 +6,9 @@ was deprecated in favor of the
 [GitLab Plugin](https://wiki.jenkins.io/display/JENKINS/GitLab+Plugin).
 Please use documentation for the new [Jenkins CI service](jenkins.md).
 
+NOTE: **Note:**
+This service was [removed in v13.0](https://gitlab.com/gitlab-org/gitlab/-/issues/1600)
+
 Integration includes:
 
 - Trigger Jenkins build after push to repo