Fix missing volume redis in Nextcloud

[Vdauphin]

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[githubsaturn]

redis doesn't have any persistent data by default unless the start command is changed.

Why is this volume needed?

[Vdauphin]

I don't know exactly but when I checked the volume of the redis docker (with docker inspect -f '{{ .Mounts }}'), it has shown a volume with random number (https://stackoverflow.com/questions/62649302/docker-run-volume-keeps-creating-random-volumes-and-not-using-the-one-specifie)
Also it seems to have a volume /data define in docker file here: https://github.com/docker-library/redis/blob/master/7.2/alpine3.18/Dockerfile#L103
The CapRover app has a volume also https://github.com/caprover/one-click-apps/blob/master/public/v4/apps/redis.yml#L5