Remove 'xen.evtchn' udev rule

This rule already gets set in linux-utils
linux-utils/udev/udev-qubes-misc.rules:KERNEL=="xen/evtchn", MODE="0660", GROUP="qubes"

misc/udev-qubes-misc.rules

@@ -1,2 +1 @@
 SUBSYSTEM=="memory", ACTION=="add", ATTR{state}=="offline", ATTR{state}="online"
-KERNEL=="xen/evtchn", MODE="0666"