We no longer need it to bridge path differences between buildbot and
LUCI, and it shouldn't be in use downstream now either.

R=machenbach@chromium.org, martiniss@chromium.org, tandrii@chromium.org, yiwzhang@google.com

Bug: 1015181
Change-Id: Iaba2100653ae9f06799d1d510bef993f7f710dc4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2220171
Auto-Submit: Robbie Iannucci <iannucci@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>