Remove bogus udev.target dep from libvirtd unit

There is no 'udev.target' unit in systemd (only 'udev.service')
yet libvirtd's unit file had a dep on one. There's no compelling
reason for a dep on udev, so remove it altogether.

Reported-by: Avi Kivity <avi@redhat.com>

daemon/libvirtd.service.in

@@ -6,7 +6,6 @@
 [Unit]
 Description=Virtualization daemon
 After=syslog.target
-After=udev.target
 After=avahi.target
 After=dbus.target
 Before=libvirt-guests.service