Remove BaseManager.cache attribute (#2309)

It doesn't exist at runtime

Author: flaeppe

django-stubs/db/models/manager.pyi

@@ -1,5 +1,5 @@
 import datetime
-from collections.abc import AsyncIterator, Callable, Collection, Iterable, Iterator, Mapping, Sequence
+from collections.abc import AsyncIterator, Collection, Iterable, Iterator, Mapping, Sequence
 from typing import Any, Generic, NoReturn, TypeVar, overload
 
 from django.db.models.base import Model
@@ -10,7 +10,6 @@ from typing_extensions import Self
 _T = TypeVar("_T", bound=Model, covariant=True)
 
 class BaseManager(Generic[_T]):
-    cache: Callable[[], Self]  # django-cacheops
     creation_counter: int
     auto_created: bool
     use_in_migrations: bool