Disable webrtc/multiple_peerconnections on win 10 laptops.

This benchmark fails ~20% of the time, and causes excessive flakiness
disable until the benchmark owner has investigated and fixed.

No-Try: True
TBR: johnchen@chromium.org
CC: qiangchen@chromium.org,mbonadei@chromium.org,phoglund@chromium.org
Bug: 1129497
Change-Id: I11b892cdcd85d578d1e3589faa3bd3c9cd5ad0bc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2426444Reviewed-by: Stephen Nusko <nuskos@chromium.org>
Reviewed-by: John Chen <johnchen@chromium.org>
Commit-Queue: Stephen Nusko <nuskos@chromium.org>
Auto-Submit: Stephen Nusko <nuskos@chromium.org>
Cr-Commit-Position: refs/heads/master@{#809784}

tools/perf/expectations.config

@@ -445,6 +445,7 @@ crbug.com/1094859 [ win ] v8.runtime_stats.top_25/https://en.wikipedia.org/* [ S
 
 # Benchmark: webrtc
 crbug.com/1051644 [ win ] webrtc/pause_play_peerconnections [ Skip ]
+crbug.com/1129497 [ win-laptop ] webrtc/multiple_peerconnections [ Skip ]
 
 ##### Perf FYI benchmarks go after here #####
 # Benchmark: loading.desktop_layout_ng