debian: preinst: remove modification of /etc/modules

modules are already handled by systemd and /lib/modules-load/qubes-*

debian/qubes-core-agent.preinst

@@ -48,11 +48,6 @@ if [ "$1" = "install" ] ; then
     # --------------------------------------------------------------------------
     update-alternatives --force --install /bin/sh sh /bin/bash 999
 
-    # --------------------------------------------------------------------------
-    # Modules setup
-    # --------------------------------------------------------------------------
-    echo "xen_netfront" >> /etc/modules
-
     # --------------------------------------------------------------------------
     # Remove `mesg` from root/.profile?
     # --------------------------------------------------------------------------