use arg_type.annotation instead of arg_type._annotation

Author: tikuma-lsuhsc

src/sphinx_autodoc_typehints/__init__.py

@@ -718,7 +718,7 @@ def _inject_signature(  # noqa: C901
     type_aliases = app.config["autodoc_type_aliases"]
 
     for arg_name, arg_type in signature.parameters.items():
-        annotation = arg_type._annotation if arg_type._annotation in type_aliases else type_hints.get(arg_name)
+        annotation = arg_type.annotation if arg_type.annotation in type_aliases else type_hints.get(arg_name)
 
         default = signature.parameters[arg_name].default