[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}

chrome/test/chromedriver/test/run_py_tests.py

@@ -136,8 +136,6 @@ _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',
 ]