[Telemetry] Disable failing smoothness.simple_mobile_sites benchmark.

This patch should be reverted when it is fixed along with a unittest to
guard against regression.

BUG=402885
NOTRY=True
TBR=epenner@chromium.org

Review URL: https://codereview.chromium.org/504163003

Cr-Commit-Position: refs/heads/master@{#291914}

tools/perf/benchmarks/smoothness.py

@@ -122,7 +122,7 @@ class SmoothnessFastPathGpuRasterizationKeySilkCases(
     silk_flags.CustomizeBrowserOptionsForFastPath(options)
 
 
-@benchmark.Enabled('android')
+@benchmark.Disabled  # crbug.com/402885
 class SmoothnessSimpleMobilePages(benchmark.Benchmark):
   """Measures rendering statistics for pinch-zooming into the tough pinch zoom
   cases