Revert "autoninja: roll back to python from python3"
Revert "autoninja: roll back to python from python3"

This reverts commit 3253a1deca587cc8dd5d83d790cea8f9654e2c33.

Reason for revert:
Blocker is fixed in https://crbug.com/1168365#c8

Original change's description:
> autoninja: roll back to python from python3
>
> python3 is currently not recognized on git bash.
> https://crrev.com/c/2629087/15#message-b5093e69201df42adb7ac643e4f97f9f366a299d
>
> This is partial revert of
> https://crrev.com/c/2629087
> https://crrev.com/c/2631396
>
> Bug: b/177465438
> Change-Id: I1b2698f5fc27144035598249c43800d25801a0f7
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2638834
> Reviewed-by: Bruce Dawson <brucedawson@chromium.org>
> Commit-Queue: Bruce Dawson <brucedawson@chromium.org>
> Commit-Queue: Takuto Ikuta <71927f930fca81015e0f496c65cd126ab1a692e3@chromium.org>
> Auto-Submit: Takuto Ikuta <71927f930fca81015e0f496c65cd126ab1a692e3@chromium.org>

Bug: b/177465438, 1168365
Change-Id: I368e28aeec9c585a96c8b44f030609eac58698f2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2752772
Reviewed-by: Dirk Pranke <6693ee08b084bb2ffa767f664c99b689395e0e4b@google.com>
Auto-Submit: Takuto Ikuta <71927f930fca81015e0f496c65cd126ab1a692e3@chromium.org>

CoherentLabs/depot_tools,CoherentLabs/depot_tools