Fix a broken test case after the Django 4.1 update. (#1093)

This fixes the CI starting occur on #1086 and following PRs due to the release
of Django 4.1 (https://docs.djangoproject.com/en/4.1/releases/4.1/) which
shipped the change

    # Even if this relation is not to pk, we require still pk value.
    # The wish is that the instance has been already saved to DB,
    # although having a pk value isn't a guarantee of that.
    if self.instance.pk is None:
        raise ValueError(
            f"{instance.__class__.__name__!r} instance needs to have a primary "
            f"key value before this relationship can be used."
        )

in https://github.com/django/django/pull/15318.

tests/typecheck/fields/test_related.yml

@@ -654,6 +654,7 @@
                     pass
                 TransactionManager = BaseManager.from_queryset(TransactionQuerySet)
                 class Transaction(models.Model):
+                    pk = 0
                     objects = TransactionManager()
                     def test(self) -> None:
                         self.transactionlog_set