Merge pull request #6698 from chris-short/slack-channel-sig-contribex-comms

Update channels.yaml

Author: k8s-ci-robot

communication/slack-config/channels.yaml

@@ -382,6 +382,7 @@ channels:
     archived: true
   - name: sig-contribex
   - name: sig-contribex-meetings
+  - name: sig-contribex-comms
   - name: sig-contribex-triage
     archived: true
   # sig-docs* channels are defined in sig-docs/