[Sheriff] Disable memory_desktop.browse:news:hackernews

Temporarily disable the test to clear the bot errors, because the
test is failing frequently/flakily due to crbug.com/749773.

TBR=nednguyen@chromium.org, adithyas@chromium.org, yutak@chromium.org
NOTRY=true

Bug: 749773
Change-Id: Ib0f919c243450c64a168f268d8e365646f2936ff
Reviewed-on: https://chromium-review.googlesource.com/595239Reviewed-by: Hiroshige Hayashizaki <hiroshige@chromium.org>
Commit-Queue: Hiroshige Hayashizaki <hiroshige@chromium.org>
Cr-Commit-Position: refs/heads/master@{#490828}

tools/perf/benchmarks/system_health_smoke_test.py

@@ -68,8 +68,9 @@ _DISABLED_TESTS = frozenset({
   # crbug.com/725386
   'benchmarks.system_health_smoke_test.SystemHealthBenchmarkSmokeTest.system_health.memory_desktop.browse:social:twitter', # pylint: disable=line-too-long
 
-  # crbug.com/749918
+  # crbug.com/749773 crbug.com/749918
   'benchmarks.system_health_smoke_test.SystemHealthBenchmarkSmokeTest.system_health.memory_mobile.load:news:cnn', # pylint: disable=line-too-long
+  'benchmarks.system_health_smoke_test.SystemHealthBenchmarkSmokeTest.system_health.memory_desktop.browse:news:hackernews', # pylint: disable=line-too-long
 })