[Sheriff] Update test expectations for scrolling web tests

overflow-scrollbar-combinations.html is flaking consistently on Linux
Tests builders.

See below for example build.
https://ci.chromium.org/p/chromium/builders/ci/Linux%20Tests/94750

Bug: 1141206
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Change-Id: I5ccb03ce75a47f3a8523a1b033b67144392d1fd6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2490850Reviewed-by: Thomas Lukaszewicz <tluk@chromium.org>
Commit-Queue: Thomas Lukaszewicz <tluk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#819637}

third_party/blink/web_tests/TestExpectations

@@ -6407,3 +6407,6 @@ crbug.com/1123116 external/wpt/permissions-policy/permissions-policy-frame-polic
 crbug.com/1123116 external/wpt/permissions-policy/permissions-policy-frame-policy-disallowed-for-all.https.sub.html [ Failure ]
 crbug.com/1140329 http/tests/devtools/network/network-filter-service-worker.js [ Pass Timeout Failure ]
 crbug.com/1140329 virtual/threaded/external/wpt/web-animations/timing-model/animations/updating-the-finished-state.html [ Pass Failure Timeout ]
+
+#Sheriff 2020-10-21
+crbug.com/1141206 scrollbars/overflow-scrollbar-combinations.html [ Pass Failure ]