Add return type of scoped_session.__call__ (#138)

* Add return type of scoped_session.__call__

* Update scoping.pyi

Author: kasium

sqlalchemy-stubs/orm/scoping.pyi

@@ -1,13 +1,15 @@
 from typing import Any
 from typing import Optional
 
+from ..orm import Session
+
 class scoped_session:
     session_factory: Any = ...
     registry: Any = ...
     def __init__(
         self, session_factory: Any, scopefunc: Optional[Any] = ...
     ) -> None: ...
-    def __call__(self, **kw: Any): ...
+    def __call__(self, **kw: Any) -> Session: ...
     def remove(self) -> None: ...
     def configure(self, **kwargs: Any) -> None: ...
     def query_property(self, query_cls: Optional[Any] = ...): ...