image_to_vm.sh: Drop virtualbox output support

This is an untested configuration that's been broken
for a while.

BUG=chromium:413960
TEST=ran image_to_vm.sh

Change-Id: I633a0f28d60e9a250f7b25903f83ec9af90ae3b7
Reviewed-on: https://chromium-review.googlesource.com/217975
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Tested-by: Gaurav Shah <gauravsh@chromium.org>
Commit-Queue: Gaurav Shah <gauravsh@chromium.org>
1 file changed