Disable CrSettingsPrivacyPageTest.All in webui_polymer2_browser_tests

Fails reliably on macOS 10.12 since
https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Mac10.12%20Tests/15035

NOTRY=true
TBR=dpapad@chromium.org, scottchen@chromium.org, rbpotter@chromium.org

Bug: 877109, 876990
Change-Id: I360d6766bffd48178894d9023fcc1758c0e7eba3
Reviewed-on: https://chromium-review.googlesource.com/1189683
Commit-Queue: Trent Apted <tapted@chromium.org>
Reviewed-by: Trent Apted <tapted@chromium.org>
Cr-Commit-Position: refs/heads/master@{#586179}

testing/buildbot/filters/webui_polymer2_browser_tests.filter

@@ -41,6 +41,9 @@
 # Mac only failure. See crbug.com/874976
 -MaterialHistoryItemTest.All
 
+# Mac only failure. See crbug.com/876990
+-CrSettingsPrivacyPageTest.All
+
 # Tests that fail only on official builds.
 -CrSettingsChromeCleanupPageTest.All
 -CrSettingsIncompatibleApplicationsPageTest.All