longhorn: upgrade to 1.10.2

Third hop towards 1.11.2. 1.10 removes the longhorn.io/v1beta1 API, which
requires every Longhorn CRD to store only v1beta2; all 22 already do (the
check from the 1.10 important notes). Settings move to a per-data-engine
JSON format, but the chart renders our defaultSettings and
defaultBackupStore values unchanged.

Checked beforehand: 17 healthy volumes plus 2 detached, no backing
images, system backup pre-upgrade-v1-9-2-202610221421 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: 1.9.2
+      targetRevision: 1.10.2
       helm:
         values: |
           persistence: