Add next to ResultProxy stub (#133)

Author: euresti

sqlalchemy-stubs/engine/result.pyi

@@ -58,6 +58,8 @@ class ResultProxy:
     def is_insert(self): ...
     def close(self) -> None: ...
     def __iter__(self) -> Iterator[RowProxy]: ...
+    def __next__(self) -> RowProxy: ...
+    def next(self) -> RowProxy: ...
     @property
     def inserted_primary_key(self): ...
     def last_updated_params(self): ...