Remove old repair steps that aren't executed anymore

lib/composer/composer/autoload_classmap.php

lib/composer/composer/autoload_static.php

lib/private/Repair.php

lib/private/Repair/NC11/CleanPreviews.php

lib/private/Repair/NC11/CleanPreviewsBackgroundJob.php

lib/private/Repair/NC11/MoveAvatars.php

lib/private/Repair/NC11/MoveAvatarsBackgroundJob.php

lib/private/Repair/NC12/InstallCoreBundle.php

lib/private/Repair/NC12/RepairIdentityProofKeyFolders.php

lib/private/Repair/NC12/UpdateLanguageCodes.php

lib/private/Server.php

tests/lib/Repair/NC11/CleanPreviewsBackgroundJobTest.php

tests/lib/Repair/NC11/CleanPreviewsTest.php

tests/lib/Repair/NC12/InstallCoreBundleTest.php

tests/lib/Repair/NC12/UpdateLanguageCodesTest.php