This reverts commit e2ac022f.

git-cache issues were solved by https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2120966

Original change's description:
> Reland "depot_tools: Run using Python 3 by default."
>
> This is a reland of 01ed3589
>
> * python_runner.sh, gclient, roll-dep and fetch will call vpython
>   (instead of vpython3) when running on Windows under git-bash.
> * vpython3 now detects when running on Windows under git-bash and
>   executes vpython3.bat instead.
> * vpython3.bat calls python3.exe directly instead of calling python3.bat.
>
> Original change's description:
> > depot_tools: Run using Python 3 by default.
> >
> > Run gclient, roll-dep, fetch and custom git commands (i.e. git-cl, git-rebase-update, git-new-branch, etc.)
> > using vpython3 by default.
> >
> > Change-Id: I4eecddafa6ca4c5f82ec097615c79d2a741613e7
> > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2113550
> > Reviewed-by: Anthony Polito <apolito@google.com>
> > Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>
>
> Change-Id: I9829141d7ea26a67e655264430151f493e73a930
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2118418
> Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>
> Reviewed-by: Anthony Polito <apolito@google.com>

Change-Id: Iff02533f0a11062f335a010c074043c720d5b2ba
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2121304Reviewed-by: Josip Sokcevic <sokcevic@google.com>
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>