Update return type of Generator.close in 3.13 (#13127)

Co-authored-by: Jelle Zijlstra <[email protected]>

Author: brianschubert

stdlib/typing.pyi

@@ -463,7 +463,11 @@ class Generator(Iterator[_YieldT_co], Generic[_YieldT_co, _SendT_contra, _Return
     @overload
     @abstractmethod
     def throw(self, typ: BaseException, val: None = None, tb: TracebackType | None = None, /) -> _YieldT_co: ...
-    def close(self) -> None: ...
+    if sys.version_info >= (3, 13):
+        def close(self) -> _ReturnT_co | None: ...
+    else:
+        def close(self) -> None: ...
+
     def __iter__(self) -> Generator[_YieldT_co, _SendT_contra, _ReturnT_co]: ...
     @property
     def gi_code(self) -> CodeType: ...