Use dnf5-compatible "group install" command
* yum knows only "yum groupinstall"
* dnf < 5 knows both
* dnf-5 only "dnf5 group install"
From RHEL5 version of yum, @group syntax is supported, so we can
replace all groupinstall commands with "install @group".
Related: https://pagure.io/koji/issue/3971