image_signing: swap_rootfs.sh: drop unused script

This script hasn't been executed by image_signing or the cros-signer
code, and cs/ doesn't turn up any hits.  Scrub it from the codebase.

BRANCH=None
BUG=chromium:714598
TEST=signing images still works

Change-Id: Ic9cf90929f949a7f6b4e41e5b819d6f786c1c833
Reviewed-on: https://chromium-review.googlesource.com/500328
Commit-Ready: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: David Riley <davidriley@chromium.org>
1 file changed