F44 Change: Enforcing signature checking by default

[travier]

See: https://fedoraproject.org/wiki/Changes/Enforcing_signature_checking_by_default

Change the RPM default package verification mode to enforcing signature checking, to follow upstream RPM 6.0 default: only packages with a verified signature can be installed, unless explicitly overridden by --nosignature or corresponding API.

I'm not fully sure this will impact rpm-ostree.

Workaround would be to ask users to sign their unsigned packages and import the GPG key locally.