Revert "Add a whitespace change to test_env.py to reset swarming deduplication."

This reverts commit 320f9516ab.

Reason for revert: deduping was reset, comment no longer needed

Original change's description:
> Add a whitespace change to test_env.py to reset swarming deduplication.
> 
> Due to emergency server maintenance in crbug.com/1069091, we need all
> tests to not be deduplicated into tests that ran prior to the
> maintenance. Adding a trivial change to //testing/test_env.py will
> prevent any task deduplication since most every test includes this file
> in its inputs.
> 
> TBR=johnchen
> 
> No-Try: true
> No-Tree-Checks: true
> Bug: 1069091
> Change-Id: If99af96b6bce7b00cd982de0234b39dbb9a9ec89
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2142619
> Commit-Queue: Ben Pastene <bpastene@chromium.org>
> Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#757517}

TBR=iannucci@chromium.org,bpastene@chromium.org,johnchen@chromium.org

Change-Id: If0b620f3461efeef34ec7a0d24fcd813f585d00b
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1069091
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2144360
Reviewed-by: Ben Pastene <bpastene@chromium.org>
Commit-Queue: Ben Pastene <bpastene@chromium.org>
Cr-Commit-Position: refs/heads/master@{#757943}

testing/test_env.py

@@ -5,9 +5,6 @@
 
 """Sets environment variables needed to run a chromium unit test."""
 
-# Whitespace change to break swarming deduplication.
-# TODO(crbug.com/1069091): Delete this comment.
-
 import io
 import os
 import signal