Disable failing rendering.mobile/microsoft_fireflies

NOTRY=true
TBR=nednguyen@google.com
CC=vmiura@chromium.org,sadrul@chromium.org

Bug: 901526
Change-Id: I27a98ceea1fd4a007a3ba99e7799584a91053cfb
Reviewed-on: https://chromium-review.googlesource.com/c/1316651Reviewed-by: Caleb Rouleau <crouleau@chromium.org>
Commit-Queue: Caleb Rouleau <crouleau@chromium.org>
Cr-Commit-Position: refs/heads/master@{#605082}

tools/perf/expectations.config

@@ -205,6 +205,7 @@ crbug.com/873013 [ Android_Webview ] rendering.mobile/yahoo_answers_mobile_2018
 crbug.com/893197 [ Nexus_5X ] rendering.mobile/yahoo_answers_mobile_2018 [ Skip ]
 crbug.com/865400 [ Pixel_2 ] rendering.mobile/yahoo_answers_mobile_2018 [ Skip ]
 crbug.com/874935 [ Nexus_5 ] rendering.mobile/yahoo_news_2018 [ Skip ]
+crbug.com/901526 [ All ] rendering.mobile/microsoft_fireflies [ Skip ]
 
 # Benchmark: rasterize_and_record_micro.top_25
 crbug.com/764543 [ All ] rasterize_and_record_micro.top_25/file://static_top_25/wikipedia.html [ Skip ]