test(integrations): Remove vacuous missing-integration test

The test_missing_integration_filtered_from_response test never exercised the
None-filtering logic it claimed to test. The Integration foreign key uses
CASCADE on_delete, so deleting the Integration also cascade-deleted the
OrganizationIntegration row, leaving zero results for the queryset. Even
bypassing CASCADE, the queryset's integration__status JOIN would exclude
orphaned rows. The test passed vacuously regardless of whether the fix
existed.

The remaining test_serialization_error_filtered_from_response properly
exercises the None-filtering by triggering a real exception in _serialize.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: leeandher

tests/sentry/integrations/api/endpoints/test_user_organizationintegration.py

@@ -2,7 +2,6 @@
 
 import orjson
 
-from sentry.integrations.models.integration import Integration
 from sentry.testutils.cases import APITestCase
 from sentry.testutils.silo import control_silo_test
 
@@ -74,19 +73,6 @@ def test_billing_users_dont_see_integrations(self) -> None:
             content = orjson.loads(response.content)
             assert content == []
 
-    def test_missing_integration_filtered_from_response(self) -> None:
-        """OrganizationIntegrations whose Integration was deleted don't produce null entries."""
-        integration = self.create_provider_integration(provider="github")
-        self.create_organization_integration(
-            organization_id=self.organization.id, integration_id=integration.id
-        )
-
-        # Delete the Integration row directly to simulate orphaned state
-        Integration.objects.filter(id=integration.id).delete()
-
-        response = self.get_success_response(self.user.id)
-        assert response.data == []
-
     def test_serialization_error_filtered_from_response(self) -> None:
         """An exception during serialization should produce an empty list, not null entries."""
         integration = self.create_provider_integration(provider="github")