Fix stubs for async generator methods (#12232)

Author: kumaraditya303

stdlib/typing.pyi

@@ -542,16 +542,18 @@ class AsyncIterator(AsyncIterable[_T_co], Protocol[_T_co]):
 class AsyncGenerator(AsyncIterator[_YieldT_co], Generic[_YieldT_co, _SendT_contra]):
     def __anext__(self) -> Awaitable[_YieldT_co]: ...
     @abstractmethod
-    def asend(self, value: _SendT_contra, /) -> Awaitable[_YieldT_co]: ...
+    def asend(self, value: _SendT_contra, /) -> Coroutine[Any, Any, _YieldT_co]: ...
     @overload
     @abstractmethod
     def athrow(
         self, typ: type[BaseException], val: BaseException | object = None, tb: TracebackType | None = None, /
-    ) -> Awaitable[_YieldT_co]: ...
+    ) -> Coroutine[Any, Any, _YieldT_co]: ...
     @overload
     @abstractmethod
-    def athrow(self, typ: BaseException, val: None = None, tb: TracebackType | None = None, /) -> Awaitable[_YieldT_co]: ...
-    def aclose(self) -> Awaitable[None]: ...
+    def athrow(
+        self, typ: BaseException, val: None = None, tb: TracebackType | None = None, /
+    ) -> Coroutine[Any, Any, _YieldT_co]: ...
+    def aclose(self) -> Coroutine[Any, Any, None]: ...
     @property
     def ag_await(self) -> Any: ...
     @property