Fix return type annotations for ast.parse (#14369)

Author: hunterhogan

stdlib/ast.pyi

@@ -1797,7 +1797,7 @@ if sys.version_info >= (3, 13):
         type_comments: bool = False,
         feature_version: None | int | tuple[int, int] = None,
         optimize: Literal[-1, 0, 1, 2] = -1,
-    ) -> AST: ...
+    ) -> mod: ...
 
 else:
     @overload
@@ -1868,7 +1868,7 @@ else:
         *,
         type_comments: bool = False,
         feature_version: None | int | tuple[int, int] = None,
-    ) -> AST: ...
+    ) -> mod: ...
 
 def literal_eval(node_or_string: str | AST) -> Any: ...