This reverts commit d1d7b0a4.

Reason for revert: This seems likely the cause of infra failures for
perf builders.

Original change's description:
> Reland "Update gsutil to use gsutil version 5.6, python3"
>
> This is a reland of commit c0af61c8
>
> Original change's description:
> > Update gsutil to use gsutil version 5.6, python3
> >
> > R=gavinmak@google.com
> >
> > Bug: 1184108
> > Change-Id: I933c07132006b731a97153080ebe86ed756fbdb2
> > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3497998
> > Reviewed-by: Gavin Mak <gavinmak@google.com>
> > Commit-Queue: Josip Sokcevic <sokcevic@google.com>
>
> Bug: 1184108
> Change-Id: I72c5b967f52e8b4531c238b20444596c549a5726
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3502172
> Reviewed-by: Gavin Mak <gavinmak@google.com>
> Commit-Queue: Josip Sokcevic <sokcevic@google.com>

Bug: 1184108
Change-Id: Iad314a3b6147f460e2f301481b03c5d3d7d601db
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3503959
Auto-Submit: Garrett Beaty <gbeaty@google.com>
Reviewed-by: Josip Sokcevic <sokcevic@google.com>
Commit-Queue: Josip Sokcevic <sokcevic@google.com>