[nextcloud] Update Helm chart redis to v15 (#833)

Co-authored-by: Renovate Bot <bot@renovateapp.com>

charts/incubator/nextcloud/Chart.yaml

@@ -11,7 +11,7 @@ dependencies:
 - condition: redis.enabled
   name: redis
   repository: https://charts.bitnami.com/bitnami
-  version: 14.8.11
+  version: 15.0.3
 deprecated: false
 description: A private cloud server that puts the control and security of your own
   data back into your hands.
@@ -33,4 +33,4 @@ sources:
 - https://github.com/nextcloud/docker
 - https://github.com/nextcloud/helm
 type: application
-version: 2.3.4
+version: 3.0.0