[Sheriff] Disable HistoryMetricsTest.All

TBR=msramek@chromium.org

Bug: 1000573
Change-Id: I2b6d67d122e146656de28ef5b33bc42137a33833
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1782846Reviewed-by: Jan Wilken Dörrie <jdoerrie@chromium.org>
Reviewed-by: Martin Šrámek <msramek@chromium.org>
Commit-Queue: Jan Wilken Dörrie <jdoerrie@chromium.org>
Cr-Commit-Position: refs/heads/master@{#693095}

chrome/test/data/webui/history/history_browsertest.js

@@ -117,7 +117,8 @@ HistoryMetricsTest.prototype = {
   ]),
 };
 
-TEST_F('HistoryMetricsTest', 'All', function() {
+// TODO(https://crbug.com/1000573): Re-enable once flakiness is fixed.
+TEST_F('HistoryMetricsTest', 'DISABLED_All', function() {
   mocha.run();
 });