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/install.bats

@@ -14,7 +14,7 @@ config() {
   [[ "$output" == *"is the deployed copy"* ]]
   [ "$(config)" = "WORKING_COPY=$(printf '%q' "$WC")" ]
   [ "$(readlink "$HOME/.local/bin/coredesktop-dev")" = "$PROJECT/bin/coredesktop-dev" ]
-  called install_packages shellcheck bats tea qemu-base qemu-hw-display-virtio-vga libisoburn
+  called install_packages shellcheck bats tea qemu-base libisoburn
 }
 
 @test "install refuses the deployed copy however it's spelled" {