common.sh: remove au-generator.zip support

We dropped au-generator.zip building a while back.  Clean up some
code in common.sh that supported that.

BUG=chromium:999596
TEST=CQ passes

Change-Id: I7807f13f576dfe71af323e38059b9f6079fd0904
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosutils/+/1763881
Tested-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Amin Hassani <ahassani@chromium.org>
Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>
1 file changed