[tools/perf] Disable load:news:washingtonpost on N5X

Flaky story in CQ.

TBR=nednguyen@google.com
NOTRY=true

Bug: 893873
Change-Id: I19c6e056ed5ba8041c70d70b1e9ce143f0dccdab
Reviewed-on: https://chromium-review.googlesource.com/c/1275430Reviewed-by: Juan Antonio Navarro Pérez <perezju@chromium.org>
Commit-Queue: Juan Antonio Navarro Pérez <perezju@chromium.org>
Cr-Commit-Position: refs/heads/master@{#598708}

tools/perf/expectations.config

@@ -280,6 +280,7 @@ crbug.com/883652 [ Android_One ] system_health.memory_mobile/browse:news:cnn:201
 crbug.com/883652 [ Android_One ] system_health.memory_mobile/browse:news:cnn [ Skip ]
 crbug.com/883652 [ Android_One ] system_health.memory_mobile/browse:news:toi [ Skip ]
 crbug.com/883652 [ Nexus_5 ] system_health.memory_mobile/browse:shopping:avito [ Skip ]
+crbug.com/893873 [ Nexus_5X ] system_health.memory_mobile/load:news:washingtonpost [ Skip ]
 
 # Benchmark: tab_switching.typical_25
 crbug.com/747026 [ Mac ] tab_switching.typical_25/multitab:misc:typical24 [ Skip ]