flatpak: Build without vala bindings
vala bindings were removed in [1] which is causing out pipelines to fail. We don't need them anyways, so disable the build options for libportal and libcloudproviders.
vala bindings were removed in [1] which is causing out pipelines to fail. We don't need them anyways, so disable the build options for libportal and libcloudproviders.