Signup providers list needs to be updated

[vdbhb59]

As being discussed here: https://help.nextcloud.com/t/list-of-hosting-providers-outdated/85677, the providers details on https://nextcloud.com/signup/ is outdated and needs to be updated. Example, owncloud is no longer offering free accounts, some of them no longer affiliate nextcloud. You can add tab.digital and operationtulip there, etc.,
@devnull can add more, or someone from the community admins can.

Meant to raise it earlier, but it slipped out of my mind, so raising it here a bit late.