Revert "Mash: Re-enable a test which may no longer be flaky."

This reverts commit b68dde46.

Reason for revert:
The test is still flaky. Fails with same error as before.
e.g.
https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/linux-chromeos-dbg/8629

Original change's description:
> Mash: Re-enable a test which may no longer be flaky.
> 
> test is ExtensionDisabledGlobalErrorTest.UninstallWhilePromptBeingShown
> 
> Bug: 883371
> Change-Id: I1ce860a5c25e9b6b791be681e98907aed9ffb9bc
> Reviewed-on: https://chromium-review.googlesource.com/c/1305873
> Reviewed-by: James Cook <jamescook@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#603591}

TBR=jamescook@chromium.org,estade@chromium.org

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

Bug: 883371
Change-Id: I7b232b609a0f60a3c68c61822871ba8dadd6109f
Reviewed-on: https://chromium-review.googlesource.com/c/1310506Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#604348}

testing/buildbot/filters/chromeos.single_process_mash.browser_tests.filter

@@ -129,6 +129,9 @@
 # Failing on ASAN bot. crbug.com/882631
 -ExtensionWebRequestApiTest.WebRequestTypes
 
+# Crashing flakily. https://crbug.com/883371
+-ExtensionDisabledGlobalErrorTest.UninstallWhilePromptBeingShown
+
 # Flaky on ASAN bot. crbug.com/884216
 -KeyboardOverlayUIBrowserTest.*