Update nextcloud dependency charts to work with k8s 1.16

openappstack!144 upgrades rke to 1.0.0 and k8s to 1.16.

Job #9390 failes with:

    in /var/lib/OpenAppStack/source/helmfiles/helmfile.d/20-nextcloud.yaml: failed processing release oas-test-files: helm exited with status 1:
      Error: [unable to recognize "": no matches for kind "StatefulSet" in version "apps/v1beta1", unable to recognize "": no matches for kind "StatefulSet" in version "apps/v1beta2"]

Turns out some api resources changed in k8s 1.16, i.e the StatefulSet api, from apps/v1beta1/apps/v1beta2 to apps. https://github.com/helm/charts/issues/7680 descibes this issue.

We need to update our nextcloud dependency charts, mainly those listed in that issue:

Impacted charts

At least, impacted charts are:

stable/rabbitmq (fixed in #7848)
stable/redis (fixed in #7686)