user_saml is shipped via appstore

Keeping it in the shipped.json leads to odd side-effects such as https://help.nextcloud.com/t/earn-a-t-shirt-by-testing-nextcloud-12-beta-2/12374/41?u=lukasreschke

 in case a previous version was installed.

Signed-off-by: Lukas Reschke <lukas@statuscode.ch>