chore(integrations): Gate disabling repositories behind a separate flag

[wedamija]

Being cautious with this auto sync work and gating a potentially destructive operation behind a deletion flag.

[github-actions]

Backend Test Failures

Failures on 0d1a644 in this run:

tests/sentry/integrations/github/tasks/test_sync_repos_on_install_change.py::SyncReposOnInstallChangeTestCase::test_mixed_add_and_remove — log

[gw1] linux -- Python 3.13.1 /home/runner/work/sentry/sentry/.venv/bin/python3
tests/sentry/integrations/github/tasks/test_sync_repos_on_install_change.py:114: in test_mixed_add_and_remove
    assert old_repo.status == ObjectStatus.DISABLED
E   AssertionError: assert 0 == 1
E    +  where 0 = <Repository at 0x7f15cc9c34d0: id=21, organization_id=4557973191393312, name='getsentry/old-repo', provider='integrations:github'>.status
E    +  and   1 = ObjectStatus.DISABLED

tests/sentry/integrations/source_code_management/test_sync_repos.py::SyncReposForOrgTestCase::test_disables_removed_repos — log

[gw1] linux -- Python 3.13.1 /home/runner/work/sentry/sentry/.venv/bin/python3
tests/sentry/integrations/source_code_management/test_sync_repos.py:94: in test_disables_removed_repos
    assert repo.status == ObjectStatus.DISABLED
E   AssertionError: assert 0 == 1
E    +  where 0 = <Repository at 0x7fa379beeb10: id=29, organization_id=4557973197553696, name='getsentry/old-repo', provider='integrations:github'>.status
E    +  and   1 = ObjectStatus.DISABLED

tests/sentry/integrations/github/test_webhook.py::InstallationRepositoriesEventWebhookTest::test_end_to_end_repos_removed — log

[gw0] linux -- Python 3.13.1 /home/runner/work/sentry/sentry/.venv/bin/python3
tests/sentry/integrations/github/test_webhook.py:500: in test_end_to_end_repos_removed
    assert repo.status == ObjectStatus.DISABLED
E   AssertionError: assert 0 == 1
E    +  where 0 = <Repository at 0x7fb1a32dd650: id=23, organization_id=4557973193359376, name='getsentry/old-repo', provider='integrations:github'>.status
E    +  and   1 = ObjectStatus.DISABLED

tests/sentry/integrations/github/tasks/test_sync_repos_on_install_change.py::SyncReposOnInstallChangeTestCase::test_repos_removed — log

[gw0] linux -- Python 3.13.1 /home/runner/work/sentry/sentry/.venv/bin/python3
tests/sentry/integrations/github/tasks/test_sync_repos_on_install_change.py:84: in test_repos_removed
    assert repo.status == ObjectStatus.DISABLED
E   AssertionError: assert 0 == 1
E    +  where 0 = <Repository at 0x7fbefe1de780: id=21, organization_id=4557973192835088, name='getsentry/old-repo', provider='integrations:github'>.status
E    +  and   1 = ObjectStatus.DISABLED