Allow user arg in APIClient.force_authenticate to be None (#367)

* Allow user arg in `APIClient.force_authenticate` to be `None`

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

rest_framework-stubs/test.pyi

@@ -74,7 +74,9 @@ class ForceAuthClientHandler(ClientHandler):
 
 class APIClient(APIRequestFactory, DjangoClient):
     def credentials(self, **kwargs: Any): ...
-    def force_authenticate(self, user: AnonymousUser | AbstractBaseUser = ..., token: Token | None = ...) -> None: ...
+    def force_authenticate(
+        self, user: AnonymousUser | AbstractBaseUser | None = ..., token: Token | None = ...
+    ) -> None: ...
     def request(self, **kwargs: Any) -> _MonkeyPatchedResponse: ...  # type: ignore[override]
     def get(self, path: str, data: _GetDataType = ..., follow: bool = ..., **extra: Any) -> _MonkeyPatchedResponse: ...  # type: ignore[override]
     def post(self, path: str, data: Any | None = ..., format: str | None = ..., content_type: str | None = ..., follow: bool = ..., **extra: Any) -> _MonkeyPatchedResponse: ...  # type: ignore[override]