[Sync::USS] Enable MC_MergeDifferentBMModelsModeratelyComplex test

This CL enables MC_MergeDifferentBMModelsModeratelyComplex bookmarks
integration test to run on USS architecture.

Bug: 516866,875239
Change-Id: Ia4c416adb118ce4ed751c4feebc70d9ae6b8b97d
Reviewed-on: https://chromium-review.googlesource.com/1193943Reviewed-by: Marc Treib <treib@chromium.org>
Commit-Queue: Mohamed Amir Yosef <mamir@chromium.org>
Cr-Commit-Position: refs/heads/master@{#588395}

chrome/browser/sync/test/integration/two_client_bookmarks_sync_test.cc

@@ -1392,7 +1392,7 @@ IN_PROC_BROWSER_TEST_P(TwoClientBookmarksSyncTestIncludingUssTests,
 }
 
 // Merge moderately complex bookmark models.
-IN_PROC_BROWSER_TEST_F(TwoClientBookmarksSyncTest,
+IN_PROC_BROWSER_TEST_P(TwoClientBookmarksSyncTestIncludingUssTests,
                        MC_MergeDifferentBMModelsModeratelyComplex) {
   ASSERT_TRUE(SetupClients()) << "SetupClients() failed.";
   DisableVerifier();