Use QEMU's standard VGA instead of virtio-vga

On Arch, -vga virtio needs qemu-hw-display-virtio-vga and also
qemu-hw-display-virtio-gpu, which that package doesn't depend on; with only
the first, QEMU segfaults at start without a message. The smoketest's VMs
are headless (or VNC), so -vga std, which qemu-base has, is enough. This
reverts 2207208's extra package and checks.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

lib/smoketest.sh

@@ -56,8 +56,6 @@ require_vm_tools() {
     command -v "$tool" &> /dev/null \
       || die "$tool isn't installed. Install coredesktop-dev's packages: bash $(sibling_dir)/update.sh"
   done
-  qemu_has_virtio_vga \
-    || die "QEMU has no virtio-vga display. Install coredesktop-dev's packages: bash $(sibling_dir)/update.sh"
   [ -r "$KVM_DEVICE" ] && [ -w "$KVM_DEVICE" ] \
     || die "Can't use $KVM_DEVICE. Turn on virtualization (VT-x/AMD-V) in the firmware settings."
 }