Merge pull request #11828 from nextcloud/enh/noid/remove-user-auth-external

chore: remove documentation for user_external

Author: blizzz

admin_manual/configuration_user/index.rst

@@ -10,7 +10,6 @@ User management
     reset_user_password
     user_password_policy
     two_factor-auth
-    user_auth_ftp_smb_imap
     user_auth_ldap
     user_auth_ldap_cleanup
     user_auth_ldap_api