vm/systemd: do not depend on proc-xen.mount (#466)

local-fs.target already covers /proc/xen

vm-systemd/qubes-sysinit.service

@@ -2,7 +2,7 @@
 Description=Init Qubes Services settings
 DefaultDependencies=no
 Before=sysinit.target
-After=local-fs.target proc-xen.mount
+After=local-fs.target
 
 [Service]
 Type=oneshot