Merge pull request #4864 from mrbobbytables/add-gh-channel

Add github-management slack channel

Author: k8s-ci-robot

communication/slack-config/channels.yaml

@@ -86,6 +86,7 @@ channels:
   - name: gimbal
   - name: github
     archived: true
+  - name: github-management
   - name: gitkube
   - name: gitops
   - name: gke