Fix mypy issues

Author: rmk135

src/dependency_injector/providers.pyi

@@ -304,7 +304,7 @@ class FactoryDelegate(Delegate):
 
 class FactoryAggregate(Provider[T]):
     def __init__(self, provider_dict: Optional[_Dict[Any, Provider[T]]] = None, **provider_kwargs: Provider[T]): ...
-    def __getattr__(self, provider_name: Any) -> Provider[T]: ...
+    def __getattr__(self, provider_name: Any) -> Factory[T]: ...
 
     @overload
     def __call__(self, provider_name: Optional[Any] = None, *args: Injection, **kwargs: Injection) -> T: ...
@@ -317,8 +317,8 @@ class FactoryAggregate(Provider[T]):
     def set_providers(self, provider_dict: Optional[_Dict[Any, Provider[T]]] = None, **provider_kwargs: Provider[T]) -> FactoryAggregate[T]: ...
 
     @property
-    def factories(self) -> _Dict[Any, Provider[T]]: ...
-    def set_factories(self, provider_dict: Optional[_Dict[Any, Provider[T]]] = None, **provider_kwargs: Provider[T]) -> FactoryAggregate[T]: ...
+    def factories(self) -> _Dict[Any, Factory[T]]: ...
+    def set_factories(self, provider_dict: Optional[_Dict[Any, Factory[T]]] = None, **provider_kwargs: Factory[T]) -> FactoryAggregate[T]: ...
 
 
 class BaseSingleton(Provider[T]):