It's generaly not useful and makes it harder to understand bot_update
logs. If we need to debug specific builders, we can set environment
variables in the recipe itself.

R=apolito@google.com

Bug: 1255228
Change-Id: I18fc6ee8cb15b30bc3a4422ddd04979189bacf64
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3221250
Commit-Queue: Anthony Polito <apolito@google.com>
Reviewed-by: Anthony Polito <apolito@google.com>