Revert of bot_update: add depot_tools to PATH so that e.g. apply_issue can be found (patchset #1 id:1 of https://codereview.chromium.org/1660943002/ )

Reason for revert:
I believe this breaks trybot patching on Windows. 

Example: https://build.chromium.org/p/tryserver.webrtc/builders/win_x64_gn_rel/builds/6811

Error: 
'E:\b\build\scripts\slave\.recipe_deps\depot_tools\python' is not recognized as an internal or external command,
operable program or batch file.

I'm speculatively reverting.

Original issue's description:
> bot_update: add depot_tools to PATH so that e.g. apply_issue can be found
> 
> BUG=437264
> 
> Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=298556

TBR=jochen@chromium.org,phajdan.jr@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=437264

Review URL: https://codereview.chromium.org/1662763003

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@298561 0039d316-1c4b-4281-b951-d872f2087c98