Fixup debian kernel command line

Fixes https://github.com/netbootxyz/netboot.xyz/issues/964

roles/netbootxyz/templates/menu/debian.ipxe.j2

@@ -76,8 +76,7 @@ goto deb_boot
 
 :deb_boot
 imgfree
-echo Boot parameters: ${install_params} -- quiet ${params}
-kernel ${debian_mirror}/${dir}/linux ${install_params} ${netcfg} ${mirrorcfg} -- quiet ${params} {{ kernel_params }}
+kernel ${debian_mirror}/${dir}/linux ${install_params} ${netcfg} ${mirrorcfg} {{ kernel_params }}
 initrd ${debian_mirror}/${dir}/initrd.gz
 echo
 echo MD5sums: