Revert "[Perf] Disable failing browse:media:imgur stories"

This reverts commit 3f73ae0f.

Reason for revert: Bug causing test failure is now fixed.

Original change's description:
> [Perf] Disable failing browse:media:imgur stories
>
> Disable the following two failing stories on Linux:
> * system_health.common_desktop/browse:media:imgur
> * system_health.memory_desktop/browse:media:imgur
>
> Notry: true
> TBR: wenbinzhang@google.com
> Bug: 1154753
> Change-Id: Ibb654a2736c14e2f74c986475ca705004dc3da16
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2570739
> Reviewed-by: John Chen <johnchen@chromium.org>
> Commit-Queue: John Chen <johnchen@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#833183}

TBR=johnchen@chromium.org,chromium-scoped@luci-project-accounts.iam.gserviceaccount.com,wenbinzhang@google.com

Bug: 1154753
Change-Id: I34b0c93e85de4c5dc040c1e1dfda708112be7eec
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2575950
Commit-Queue: John Chen <johnchen@chromium.org>
Reviewed-by: John Chen <johnchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#836237}

tools/perf/expectations.config

@@ -374,7 +374,6 @@ crbug.com/1147969 [ fuchsia ] system_health.memory_desktop/long_running:tools:gm
 crbug.com/1147969 [ fuchsia ] system_health.memory_desktop/long_running:tools:gmail-foreground [ Skip ]
 crbug.com/1147969 [ fuchsia ] system_health.memory_desktop/multitab:misc:typical24 [ Skip ]
 crbug.com/1147969 [ fuchsia ] system_health.memory_desktop/multitab:misc:typical24:2018 [ Skip ]
-crbug.com/1154753 [ linux ] system_health.memory_desktop/browse:media:imgur [ Skip ]
 crbug.com/1156571 [ mac-10.12 ] system_health.memory_desktop/browse:news:nytimes:2020 [ Skip ]
 
 # Memory dumps don't work at the moment for Google Earth, see the issue.