GitLab

Remove reference to needing to switch to the RBE backend now that it is
default, and add current needed workaround.

Change-Id: I52bcf7301c87f30258babba91ddbbff574dbd77d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2612218
Auto-Submit: Alexander Cooper <alcooper@chromium.org>
Commit-Queue: Yoshisato Yanagisawa <yyanagisawa@chromium.org>
Reviewed-by: Yoshisato Yanagisawa <yyanagisawa@chromium.org>
Cr-Commit-Position: refs/heads/master@{#840882}