[Cosmos] PermissionMode import (#34297)

* Update permission.py

* Suppress pylint

Author: annatisch

sdk/cosmos/azure-cosmos/azure/cosmos/permission.py

@@ -23,6 +23,9 @@
 """
 from typing import Any, Mapping
 
+# Keeping this import for API backcompat
+from .documents import PermissionMode  # pylint: disable=unused-import
+
 
 class Permission:
     """Represents a Permission object in the Azure Cosmos DB SQL API service.