[benchmarking] disable the flaky test...

[benchmarking] disable the flaky test system_health.memory_desktop/browse:social:tumblr_infinite_scroll:2018

The test has been flaky and will be disabled for now.

Bug: chromium:1068684
Change-Id: I2ad1ffe7554d626b1ce998b4a3e259ef971dcd98
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2153308
Commit-Queue: Wenbin Zhang <wenbinzhang@google.com>
Reviewed-by: John Chen <johnchen@chromium.org>
Reviewed-by: Timothy Dresser <tdresser@chromium.org>
Cr-Commit-Position: refs/heads/master@{#759751}

tools/perf/expectations.config

@@ -348,6 +348,7 @@ crbug.com/1017290 [ linux ] system_health.memory_desktop/browse:search:google_in
 crbug.com/1017244 [ desktop ] system_health.memory_desktop/browse_accessibility:media:youtube [ Skip ]
 crbug.com/1017346 [ desktop ] system_health.memory_desktop/browse:media:youtube:2019 [ Skip ]
 crbug.com/1042632 [ win ] system_health.memory_desktop/load:tools:gmail:2019 [ Skip ]
+crbug.com/1042632 [ win ] system_health.memory_desktop/browse:social:tumblr_infinite_scroll:2018 [ Skip ]
 
 # Memory dumps don't work at the moment for Google Earth, see the issue.
 crbug.com/1057035 system_health.memory_desktop/browse:tools:earth:2020 [ Skip ]