chore(deps): update redis docker tag to v21

Author: renovate[bot]

charts/nextcloud/Chart.yaml

@@ -36,7 +36,7 @@ dependencies:
   repository: oci://registry-1.docker.io/bitnamicharts
   condition: mariadb.enabled
 - name: redis
-  version: 20.6.1
+  version: 21.1.5
   repository: oci://registry-1.docker.io/bitnamicharts
   condition: redis.enabled
 - name: collabora-online