fix: typing issue in Python 3.9 and earlier (#3431)

Author: zewenli98

py/torch_tensorrt/dynamo/conversion/_ConverterRegistry.py

@@ -519,7 +519,7 @@ def __contains__(self, key: Target | Node) -> bool:
     def get_all_converters_with_target(
         self, key: Target, return_registry_info: bool = False
     ) -> Tuple[
-        List[Any], Dict[str, int] | None
+        Union[List[Any], Dict[str, int], None]
     ]:  # TODO: Narrow to ConverterImplSignature this when we can remove FX converters
         """Get all converters across all registries for the target
 

py/torch_tensorrt/dynamo/runtime/_MutableTorchTensorRTModule.py

@@ -252,7 +252,7 @@ def forward(a, b, c=0, d=0):
 
         self.refit_state.set_state(RefitFlag.NEEDS_RECOMPILE)
 
-    def _get_total_dynamic_shapes(self) -> dict[str, Any] | None:
+    def _get_total_dynamic_shapes(self) -> Union[dict[str, Any], None]:
         if not self.arg_dynamic_shapes and not self.kwarg_dynamic_shapes:
             return None
         total_dynamic_shape = {}