unprotect grub2-tools-minimal before purging foreman

grub2-tools-minimal gets installed when we install cockpit, and
uninstalling foreman tries to uninstall grub2-tools-minimal as there are
no more dependencies on it, but that fails as it's a protected package

given this is only a test setup in a container, we don't care about grub
at all and can safely purge it again

spec/support/acceptance/purge.rb

@@ -1,6 +1,7 @@
 def purge_foreman
   case fact('osfamily')
   when 'RedHat'
+    on default, 'rm -f /etc/dnf/protected.d/grub2-tools-minimal.conf'
     on default, 'yum -y remove foreman*'
   when 'Debian'
     on default, 'apt-get purge -y foreman*', { :acceptable_exit_codes => [0, 100] }