Merge branch 'renovate/cert-manager-1.x' into 'master'

Update Helm release cert-manager to v1.6.0

See merge request openappstack/openappstack!565

flux2/core/base/cluster-issuer/cluster-issuer.yaml

 ---
-apiVersion: cert-manager.io/v1alpha2
+apiVersion: cert-manager.io/v1
 kind: ClusterIssuer
 metadata:
   name: letsencrypt-issuer

flux2/infrastructure/cert-manager/release.yaml

@@ -10,7 +10,7 @@ spec:
       # https://artifacthub.io/packages/helm/cert-manager/cert-manager
       # renovate: registryUrl=https://charts.jetstack.io
       chart: cert-manager
-      version: v1.5.4
+      version: v1.6.0
       sourceRef:
         kind: HelmRepository
         name: jetstack