Remove Sentry superuser GraphQL endpoint and privilege flag

[drazisil-codecov]

]## Summary

• Removes the should_use_sentry_app privilege flag from codecov_auth/constants.py and all references throughout the codebase
• Removes the Sentry superuser GraphQL endpoint and associated view/URL routing
• Cleans up middleware, mutation helpers, and service layer code that relied on the Sentry superuser privilege

Test plan

• Verify existing tests pass with Sentry superuser logic removed
• Confirm GraphQL schema no longer exposes the Sentry endpoint
• Check that normal user flows are unaffected