Disable a system_health.common_desktop case on Win7

system_health.common_desktop/browse:social:tumblr_infinite_scroll:2018
is failing consistently on Win7. Disabling it.

TBR=crouleau@chromium.org
NOTRY=true

Bug: 958422
Change-Id: Id2ab551bb91a3819fb15f7444ec81f99e03fda55
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1594801Reviewed-by: John Chen <johnchen@chromium.org>
Commit-Queue: John Chen <johnchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#656392}

tools/perf/expectations.config

@@ -238,6 +238,7 @@ crbug.com/903417 [ Win ] system_health.common_desktop/long_running:tools:gmail-f
 crbug.com/911214 [ Win ] system_health.common_desktop/multitab:misc:typical24 [ Skip ]
 crbug.com/934270 [ Win ] system_health.common_desktop/multitab:misc:typical24:2018 [ Skip ]
 crbug.com/931185 [ Win_7 ] system_health.common_desktop/browse:media:youtubetv:2019 [ Skip ]
+crbug.com/958422 [ Win_7 ] system_health.common_desktop/browse:social:tumblr_infinite_scroll:2018 [ Skip ]
 
 # Benchmark: system_health.common_mobile
 crbug.com/914390 [ Nexus_5 ] system_health.common_mobile/browse:chrome:newtab [ Skip ]