Fix Connection.connection to return _ConnectionFairy as documented (#216)

https://docs.sqlalchemy.org/en/14/core/connections.html#sqlalchemy.engine.Connection.connection

Author: rouge8

sqlalchemy-stubs/engine/base.pyi

@@ -22,6 +22,7 @@ from .._typing import _ExecuteOptions
 from .._typing import _ExecuteParams
 from ..exc import StatementError
 from ..pool import Pool
+from ..pool.base import _ConnectionFairy
 
 _T = TypeVar("_T")
 _T_co = TypeVar("_T_co", covariant=True)
@@ -64,7 +65,7 @@ class Connection(_ConnectionTypingCommon, Connectable):
     def execution_options(self: _TConnection, **opt: Any) -> _TConnection: ...
     def get_execution_options(self) -> _ExecuteOptions: ...
     @property
-    def connection(self) -> _DBAPIConnection: ...
+    def connection(self) -> _ConnectionFairy: ...
     def get_isolation_level(self) -> Any: ...
     @property
     def info(self) -> MutableMapping[Any, Any]: ...