Disable outdated validate_openstack pipeline

PROD-34344

Change-Id: If362fca85f4263517bcbb7f4787799085f6bb8a8
diff --git a/jenkins/client/job/validate.yml b/jenkins/client/job/validate.yml
index 92d369c..aeb9553 100644
--- a/jenkins/client/job/validate.yml
+++ b/jenkins/client/job/validate.yml
@@ -21,6 +21,8 @@
             artifact:
               keep_num: 50
           concurrent: false
+          disabled: true
+          description: "Pipeline is outdated and no longer supported. Please do not use in production"
           scm:
             type: git
             url: "${_param:jenkins_gerrit_url}/mk/mk-pipelines"