longhorn: upgrade to 1.9.2

Second hop towards 1.11.2. 1.9 stops serving longhorn.io/v1beta1 (nothing
in this repo uses it) and renames orphan-auto-deletion (false here) to
orphan-resource-auto-deletion during the upgrade. Chart values are
unchanged from 1.8.2.

Checked beforehand: 17 healthy volumes plus 2 detached, no backing
images, every Longhorn CRD already stores only v1beta2, and system backup
pre-upgrade-v1-8-2-202610221408 is Ready.

apps/templates/longhorn-helm.yaml

@@ -17,7 +17,7 @@ spec:
     - chart: longhorn
       repoURL: https://charts.longhorn.io/
       # One minor at a time up to 1.11.2, see docs/upgrade-k8s-1.33.md
-      targetRevision: 1.8.2
+      targetRevision: 1.9.2
       helm:
         values: |
           persistence: