Revert of bot_update: ensure correct depot_tools checkout is used. (patchset #2 id:20001 of https://codereview.chromium.org/2346973003/ )

Reason for revert:
broke win_chromium_x64_rel_ng/builds/281022
because of apply_issue.bat calls local python.

Original issue's description:
> bot_update: ensure correct depot_tools checkout is used.
>
> R=vadimsh@chromium.org,martiniss@chromium.org
> BUG=635641,647446
>
> Committed: https://chromium.googlesource.com/chromium/tools/depot_tools/+/972ac5040176acd90c8a1ce412f75d19f77cc4e8

TBR=martiniss@chromium.org,vadimsh@chromium.org,iannucci@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=635641,647446

Review-Url: https://codereview.chromium.org/2349673002