SQLAlchemy: Remove some implementation details (#9492)

Stubs for the mypy plugin, which aren't useful if you're using typeshed's SQLAlchemy stubs, have been removed.

Author: Avasam

stubs/SQLAlchemy/sqlalchemy/ext/mypy/__init__.pyi

@@ -1,19 +1,10 @@
 import asyncio as asyncio
 from collections.abc import Callable, Coroutine
 from typing import Any
-from typing_extensions import TypeAlias
 
 from .langhelpers import memoized_property
 
-_Greenlet: TypeAlias = Any  # actually greenlet.greenlet
-
 def is_exit_exception(e): ...
-
-class _AsyncIoGreenlet(_Greenlet):
-    driver: Any
-    gr_context: Any
-    def __init__(self, fn, driver) -> None: ...
-
 def await_only(awaitable: Coroutine[Any, Any, Any]) -> Any: ...
 def await_fallback(awaitable: Coroutine[Any, Any, Any]) -> Any: ...
 async def greenlet_spawn(fn: Callable[..., Any], *args, _require_await: bool = ..., **kwargs) -> Any: ...