Revert "[chromium] Re-enable testGetSessions"

This reverts commit 68c28c5c.

Reason for revert: Test flakiness
Original change's description:
> [chromium] Re-enable testGetSessions
> 
> Retried locally on Mac and Linux, the test seems fine.
> 
> Bug: chromium:899919
> Change-Id: I48d50f2f25a7111d4713b1b826eca36893e03289
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2236886
> Auto-Submit: Shengfa Lin <shengfa@google.com>
> Commit-Queue: Shengfa Lin <shengfa@google.com>
> Commit-Queue: John Chen <johnchen@chromium.org>
> Reviewed-by: John Chen <johnchen@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#776318}

TBR=johnchen@chromium.org,shengfa@google.com

Change-Id: Idcfbd0cbf2f46210e4c81752c693fccab5dbdecc
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: chromium:899919
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2237648
Auto-Submit: Shengfa Lin <shengfa@google.com>
Reviewed-by: John Chen <johnchen@chromium.org>
Commit-Queue: John Chen <johnchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#776528}

chrome/test/chromedriver/test/run_py_tests.py

@@ -136,6 +136,8 @@ _INTEGRATION_NEGATIVE_FILTER = [
     'HeadlessInvalidCertificateTest.*',
     # Similar issues with HeadlessChromeDriverTest.
     'HeadlessChromeDriverTest.*',
+    # Flaky: https://crbug.com/899919
+    'SessionHandlingTest.testGetSessions',
     # Flaky due to occasional timeout in starting Chrome
     'ZChromeStartRetryCountTest.testChromeStartRetryCount',
 ]