Revert "Add fury slack channel"

The fury slack channel name clashes with a user of the same name.
Channels and usernames share the same namespace and cannot co-exist.

communication/slack-config/channels.yaml

@@ -78,7 +78,6 @@ channels:
   - name: flink-operator
   - name: fr-events
   - name: fr-users
-  - name: fury
   - name: garden
   - name: garden-dev
   - name: gardener