Revert "[chromium] Enable ChromeDriver log for WPT tests"

This reverts commit cf0f02ca.

Reason for revert: may be the cause of crbug.com/1127106
(linux-blink-rel failure in webdriver_tests_suite)

Original change's description:
> [chromium] Enable ChromeDriver log for WPT tests
>
> Enable chromedriver log for CI wpt tests
>
> Change-Id: I02d4acb627ca90233b7c0dab401c7c28e6759604
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2402319
> Reviewed-by: John Chen <johnchen@chromium.org>
> Reviewed-by: Scott Violet <sky@chromium.org>
> Commit-Queue: Shengfa Lin <shengfa@google.com>
> Cr-Commit-Position: refs/heads/master@{#805817}

TBR=sky@chromium.org,johnchen@chromium.org,kyleju@chromium.org,shengfa@google.com
Bug: 1127106

No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Change-Id: I0ca84f034e92e8858cd4fcf23bb49b0e52161f75
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2404158Reviewed-by: Xianzhu Wang <wangxianzhu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#805958}

testing/buildbot/gn_isolate_map.pyl

@@ -523,7 +523,6 @@
       "../../chrome/test/chromedriver/test/run_webdriver_tests.py",
       "-v",
       "--chromedriver=chromedriver",
-      "--log-path=${ISOLATED_OUTDIR}/chromedriver.log",
       "--output-dir=${ISOLATED_OUTDIR}",
       "--test-path=../../third_party/blink/web_tests/external/wpt/webdriver/tests/",
     ],