Revert "Disable failing blink_perf.events story on 5X webview"

This reverts commit 9f907acb.

Reason for revert: The cause of the failures has (hopefully) been fixed.

Original change's description:
> Disable failing blink_perf.events story on 5X webview
> 
> NOTRY=true
> TBR=nednguyen@chromium.org
> 
> Bug: 851539
> Change-Id: I2128758cdc151cf496ee9485d9f639641bb48c69
> Reviewed-on: https://chromium-review.googlesource.com/1095636
> Commit-Queue: Charlie Andrews <charliea@chromium.org>
> Reviewed-by: Charlie Andrews <charliea@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#566040}

Bug: 851539
Change-Id: I46cfb5ff14395207d25c4b1d05bdc479fadcdd47
Reviewed-on: https://chromium-review.googlesource.com/1112517Reviewed-by: Ned Nguyen <nednguyen@google.com>
Commit-Queue: Ned Nguyen <nednguyen@google.com>
Cr-Commit-Position: refs/heads/master@{#570138}

tools/perf/expectations.config

@@ -30,7 +30,6 @@ crbug.com/853738 [ Android_Webview ] blink_perf.canvas/upload-video-to-texture.h
 
 # Benchmark: blink_perf.events
 crbug.com/799184 [ Android_One ] blink_perf.events/EventsDispatchingInShadowTrees.html [ Skip ]
-crbug.com/851539 [ Nexus5X_Webview ] blink_perf.events/EventsDispatchingInShadowTrees.html [ Skip ]
 
 # Benchmark: blink_perf.layout
 crbug.com/551950 [ Android_Svelte ] blink_perf.layout/* [ Skip ]