--no-gpgchecks was introduced in 9204838724 but is only available in
dnf5. Use --nogpgcheck instead, which is supported by both dnf4 and
dnf5 (where it is an alias for --no-gpgchecks).
Fixes test failure on distros still using dnf4 (e.g. CentOS/RHEL 9).
Co-developed-by: Claude <claude@anthropic.com>