Telemetry: Disable loading.desktop/Kenh14 on Linux and Mac

Disable due to failings on linux-perf, Mojo Linux Perf, and
mac-10_13_laptop_high_end-perf.

See bug for sample builds.

Bug: 852980
Change-Id: Ifa31ba1b34d561afc12c545a8e01e1581b4b2e68
Reviewed-on: https://chromium-review.googlesource.com/1101836Reviewed-by: Kouhei Ueno <kouhei@chromium.org>
Commit-Queue: Chong Zhang <chongz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#567498}

tools/perf/expectations.config

@@ -82,6 +82,7 @@ crbug.com/805115 [ All ] loading.desktop/goo.ne.jp [ Skip ]
 crbug.com/805115 [ All ] loading.desktop/MLB [ Skip ]
 crbug.com/805115 [ All ] loading.desktop/FDA [ Skip ]
 crbug.com/837415 [ All ] loading.desktop/NatGeo [ Skip ]
+crbug.com/852980 [ Linux Mac ] loading.desktop/Kenh14 [ Skip ]
 
 # Benchmark: loading.mobile
 crbug.com/676612 [ Nexus6_Webview ] loading.mobile/* [ Skip ]
@@ -503,3 +504,4 @@ crbug.com/805115 [ All ] loading.desktop.network_service/MLB [ Skip ]
 crbug.com/805115 [ All ] loading.desktop.network_service/FDA [ Skip ]
 crbug.com/837415 [ All ] loading.desktop.network_service/NatGeo [ Skip ]
 crbug.com/851171 [ All ] loading.desktop.network_service/Elmundo [ Skip ]
+crbug.com/852980 [ Linux ] loading.desktop.network_service/Kenh14 [ Skip ]