Set Nextcloud cronjob securityContext to run as www-data

[vshnbot]

Summary

The cronjob was failing because it runs as root (uid 0) but config.php is owned by www-data (uid 33):

Console has to be executed with the user that owns the file config/config.php
Current user id: 0
Owner id of config.php: 33

On vanilla Kubernetes explicitly set runAsUser/runAsGroup to 33.
On OpenShift leave empty to let SCC handle UID assignment.

Ref: nextcloud/helm#740

Checklist

• Update tests.
• Link this PR to related issues.
• Merge with /merge comment.

Link: vshn/appcat#589