Update README.md

dead link in corrected

Author: wtempel

modules/file-system/pre-existing-network-storage/README.md

@@ -9,7 +9,7 @@ The pre-existing network storage can be referenced in the same way as any Cluste
 Toolkit supported file-system such as [filestore](../filestore/README.md).
 
 For more information on network storage options in the Cluster Toolkit, see
-the extended [Network Storage documentation](../../../../docs/network_storage.md).
+the extended [Network Storage documentation](../../../docs/network_storage.md).
 
 ### Example