Do not use underscores in PSR4 namespaces of the backup codes app

apps/twofactor_backupcodes/appinfo/info.xml

...ofactor_backupcodes/lib/Controller/SettingsController.php

apps/twofactor_backupcodes/lib/Db/BackupCode.php

apps/twofactor_backupcodes/lib/Db/BackupCodeMapper.php

...wofactor_backupcodes/lib/Provider/BackupCodesProvider.php

apps/twofactor_backupcodes/lib/Service/BackupCodeStorage.php

...backupcodes/tests/Integration/Db/BackupCodeMapperTest.php

...codes/tests/Integration/Service/BackupCodeStorageTest.php

...kupcodes/tests/Unit/Controller/SettingsControllerTest.php

...ckupcodes/tests/Unit/Provider/BackupCodesProviderTest.php

..._backupcodes/tests/Unit/Service/BackupCodeStorageTest.php

tests/lib/Authentication/TwoFactorAuth/ManagerTest.php