chromeos: Enable app list mash_browser_tests

They pass now, probably thanks to the app list code moving into //ash.

Bug: none
Test: browser_tests --enable-features=Mash
Change-Id: I10bbdce9f5eb8bc4235f086488733a78bbbb3942
Reviewed-on: https://chromium-review.googlesource.com/1072827Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: James Cook <jamescook@chromium.org>
Cr-Commit-Position: refs/heads/master@{#561857}

testing/buildbot/filters/mash.browser_tests.filter

@@ -21,14 +21,6 @@
 # both of which use ash::Shell.
 -WizardControllerKioskFlowTest.*
 
-# Uses ash::Shell::GetRootWindowForNewWindows to choose a display for the app list.
-# More generally, app list needs to move into ash.
--AppListControllerGuestModeBrowserTest.*
--AppListControllerSearchResultsBrowserTest.*
--AppListServiceImplBrowserTest.*
--AppListTest.*
--ArcAppUninstallDialogViewBrowserTest.*
-
 # Accesses ash::Shelf to make assertions about the shelf view.
 -ArcAppDeferredLauncherBrowserTest.*
 -ArcAppDeferredLauncherWithParamsBrowserTestInstance/ArcAppDeferredLauncherWithParamsBrowserTest.*