This reverts commit bc93924b.

Reason for revert: https://crbug.com/1308393

Original change's description:
> Add VPYTHON_BYPASS support for vpython on Windows
>
> At Postman, we use a custom build of Electron which is built using a set
> of tools that are managed by us. Till now, we were using the
> VPYTHON_BYPASS environment variable to use our own managed version of
> Python on macOS but unfortunately, on Windows, depot_tools doesn't
> respect the value of this variable, so this change adds support for that
> on Windows too.
>
> Signed-off-by: Darshan Sen <raisinten@gmail.com>
> Change-Id: I63da0495463ace87d34c3c6fad1c03dee108d14b
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3525642
> Reviewed-by: Josip Sokcevic <sokcevic@google.com>
> Commit-Queue: Josip Sokcevic <sokcevic@google.com>

Bug: 1308393
Change-Id: I8cea8827e185d516b8f860b2aa8a8f21a75a8b1e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3539039
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Commit-Queue: Josip Sokcevic <sokcevic@google.com>