Merge pull request #1221 from lsst-it/renovate/rook-ceph-1.x

Update Helm release rook-ceph to v1.18.6

Author: jhoblitt

fleet/lib/rook-ceph/fleet.yaml

@@ -8,7 +8,7 @@ helm:
   chart: *name
   releaseName: *name
   repo: https://charts.rook.io/release
-  version: v1.18.4
+  version: v1.18.6
   valuesFiles:
     - values.yaml
   timeoutSeconds: 60