devserver: Deprecate update payload generation

We don't use devserver for payload generation anymore. Deprecate all
related codes.

BUG=chromium:872441
TEST=devserver_integration_test.py

Change-Id: I7c9329952c6dae96db1923fa41d811b8bd29c48c
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/1826049
Commit-Queue: Amin Hassani <ahassani@chromium.org>
Tested-by: Amin Hassani <ahassani@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
3 files changed