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>

tests/update.bats

@@ -7,7 +7,7 @@ HOOK_MARKER="# Installed by coredesktop-dev; remove with: coredesktop-dev hooks
 @test "update installs the packages and links the command, without asking anything" {
   run bash "$PROJECT/update.sh" < /dev/null
   [ "$status" -eq 0 ]
-  called install_packages shellcheck bats tea qemu-base qemu-hw-display-virtio-vga libisoburn
+  called install_packages shellcheck bats tea qemu-base libisoburn
   [ "$(readlink "$HOME/.local/bin/coredesktop-dev")" = "$PROJECT/bin/coredesktop-dev" ]
 }