Revert "Disable a flaky perf test"

This reverts commit 023e6975.

Reason for revert: The underlying Chrome bug was fixed. See the linked bug.

Original change's description:
> Disable a flaky perf test
> 
> Disable flaky system_health.memory_desktop/browse:news:hackernews:2018
> on desktop perf bots.
> 
> TBR=crouleau@chromium.org
> NOTRY=true
> 
> Bug: 1008028
> Change-Id: I15b7f313a9c409c1b7a107c4a1f22f5f057d9570
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1826995
> Commit-Queue: John Chen <johnchen@chromium.org>
> Reviewed-by: John Chen <johnchen@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#700309}

TBR=crouleau@chromium.org,johnchen@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 1008028
Change-Id: Iff1b183c08092f6727fc884186f082063619a892
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1849891Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Caleb Rouleau <crouleau@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#709531}

tools/perf/expectations.config

@@ -347,7 +347,6 @@ crbug.com/942952 [ chromeos ] system_health.memory_desktop/browse:news:hackernew
 crbug.com/959418 [ chromeos ] system_health.memory_desktop/long_running:tools:gmail-background [ Skip ]
 crbug.com/959418 [ chromeos ] system_health.memory_desktop/load:games:spychase:2018 [ Skip ]
 crbug.com/959418 [ chromeos ] system_health.memory_desktop/long_running:tools:gmail-foreground [ Skip ]
-crbug.com/1008028 [ desktop ] system_health.memory_desktop/browse:news:hackernews:2018 [ Skip ]
 crbug.com/1009838 [ mac ] system_health.memory_desktop/browse:tools:maps:2019 [ Skip ]
 crbug.com/1008001 [ win ] system_health.memory_desktop/browse:tools:sheets:2019 [ Skip ]
 crbug.com/1017290 [ linux ] system_health.memory_desktop/browse:search:google_india:2018 [ Skip ]