[onnx] Fix type on create_module() in onnx_importer.py. (llvm#2968)

The type returned was changed in
llvm#2795. This led to errors in the
downstream IREE project: iree-org/iree#16622.

python/torch_mlir/extras/onnx_importer.py

@@ -99,12 +99,12 @@ def __init__(self, model_proto: onnx.ModelProto, *, config: Config = Config()):
         assert model_proto.graph, "Model must contain a main Graph"
         self.main_graph = GraphInfo(self, model_proto.graph)
 
-    def create_module(self, context: Optional[Context] = None) -> Operation:
+    def create_module(self, context: Optional[Context] = None) -> Module:
         if not context:
             context = Context()
-        module_op = Module.create(Location.unknown(context))
+        module = Module.create(Location.unknown(context))
         # TODO: Populate module level metadata from the ModelProto
-        return module_op
+        return module
 
 
 class GraphInfo: