Resolve "Upgrade applications"

Closes #599 (closed)

The upgrade of cert-manager to 0.15.0 breaks the old version of cert-manager installed, because helm will now (again?) manage the CRDs, which helm 3 should be good at. Let's hope it works well from now on 🙏

This means that the master CI machine needs to be removed before merging this, so it won't get into trouble.

Apart from that it will also break krew. If you're determined to keep your existing cluster, run this to upgrade krew:

kubectl krew upgrade

Related:

• Release 0.4.0: #583 (closed)
• Nextcloud update: nextcloud!30 (merged)
• WordPress release: https://code.greenhost.net/open/wordpress-helm/-/merge_requests/50 (merged)