chore(autofix): Remove unneeded seat based seer check

[Zylphrex]

This check already exists on the frontend, no need to check it twice. This also lets us use to for non seat based seer plans.

[github-actions]

Backend Test Failures

Failures on a6f7325 in this run:

tests/sentry/seer/endpoints/test_group_autofix_setup_check.py::GroupAIAutofixEndpointSuccessTest::test_autofix_automation_tuning_non_seat_based — log

tests/sentry/seer/endpoints/test_group_autofix_setup_check.py:284: in test_autofix_automation_tuning_non_seat_based
    assert response.data["autofixEnabled"] is False
E   assert True is False