Disable two system health smoke tests.

Tbr: crouleau@chromium.org,nednguyen@google.com,perezju@chromium.org
Bug: 903849
Change-Id: I2821fc28f5c63a036d563a6350db4659c4fb5440
Reviewed-on: https://chromium-review.googlesource.com/c/1334831Reviewed-by: John Budorick <jbudorick@chromium.org>
Commit-Queue: John Budorick <jbudorick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607884}

tools/perf/benchmarks/system_health_smoke_test.py

@@ -107,6 +107,10 @@ _DISABLED_TESTS = frozenset({
 
   # crbug.com/893615
   'system_health.memory_desktop/multitab:misc:typical24:2018',
+
+  # crbug.com/903849
+  'system_health.memory_mobile/browse:news:cnn:2018',
+  'system_health.memory_mobile/load:games:spychase',
 })