Fix pyre errors (#13202)

Summary:
Pull Request resolved: #13202

attempt to fix
```
    [executorch/exir/backend/test/demos/rpc/executor_backend_partitioner.py:68:19] Undefined attribute [16]: `None` has no attribute `op`.
    [executorch/exir/backend/test/demos/rpc/executor_backend_partitioner.py:69:20] Undefined attribute [16]: `None` has no attribute `meta`.
    [executorch/exir/backend/test/test_backends_nested.py:200:20] Undefined attribute [16]: `None` has no attribute `meta`.
```

in D79768387

Reviewed By: cccclai, JacobSzwejbka

Differential Revision: D79828275

Author: izaitsevfb

exir/backend/test/demos/rpc/executor_backend_partitioner.py

@@ -66,6 +66,7 @@ def partition(self, edge_exported_program: ExportedProgram) -> PartitionResult:
 
                 # Tag the delegate submodules
                 if node.args[0].op == "get_attr":
+                    # pyre-ignore[16]: node.args[0] is checked above but Pyre can't infer it
                     node.args[0].meta["delegation_tag"] = delegation_tag
 
         return PartitionResult(