This reverts commit 245337d6.

Reason for revert: broke presubmit builders running run_presubmit.py recipe.

Original change's description:
> Pass target branch from tryserver in bot_update module
> 
> Change-Id: I9d250c87355833ddc6c7d8f41e9e43575713925f
> 
> Recipe-Nontrivial-Roll: build_limited_scripts_slave
> Recipe-Nontrivial-Roll: skia
> Recipe-Nontrivial-Roll: infra
> Recipe-Nontrivial-Roll: build
> Recipe-Nontrivial-Roll: release_scripts
> Change-Id: I9d250c87355833ddc6c7d8f41e9e43575713925f
> Reviewed-on: https://chromium-review.googlesource.com/c/1420977
> Commit-Queue: William Hesse <whesse@google.com>
> Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>

TBR=whesse@google.com,ehmaldonado@chromium.org

Change-Id: I89513b5bb053788291e79340c1685189adc794ec
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/1484655Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>
Commit-Queue: Andrii Shyshkalov <tandrii@chromium.org>