Docs: add missing permissions for PVC

Author: un-def

docs/docs/concepts/backends.md

@@ -1102,8 +1102,11 @@ projects:
     - apiGroups: [""]
       resources: ["nodes"]
       verbs: ["list", "get"]
+    - apiGroups: [""]
+      resources: ["persistentvolumeclaims"]
+      verbs: ["get", "create", "delete"]
     ```
-    
+
     Ensure you've created a ClusterRoleBinding to grant the role to the user or the service account you're using.
 
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