flatpak: Disable some irrelevant g-o-a options
The gnome-online-accounts (g-o-a) build is failing in the CI due to some missing dependency (libkeyutils) for the Fedora backend. Since the Fedora backend doesn't actually matter for GNOME Contacts, we can just fix the problem by not building it.
While we're at it, we can also turn off some other compile options that aren't needed either for Contacts.