remove "twoFactorAuthEnabled" from preferences. Kill switches for all code that references them (easier for refactor)

tests/Feature/Controllers/Admin/UserControllerTest.php

@@ -102,6 +102,7 @@ class UserControllerTest extends TestCase
      */
     public function testIndex(): void
     {
+        die('this test references old 2FA code.');
         $repository = $this->mock(UserRepositoryInterface::class);
         $repository->shouldReceive('hasRole')->withArgs([Mockery::any(), 'owner'])->times(3)->andReturn(true);
         $user = $this->user();