Revert "Reland "Disable flaky ShouldKeepLocalDataOnTypeMismatch_E2ETest.""

This reverts commit 9d925716.

Reason for revert: a deflaking attempt has landed prior to this
patch, hoping that the test is no longer flaky.

Original change's description:
> Reland "Disable flaky ShouldKeepLocalDataOnTypeMismatch_E2ETest."
> 
> This is a reland of c7dc2cd8
> 
> Original change's description:
> > Disable flaky ShouldKeepLocalDataOnTypeMismatch_E2ETest.
> > 
> > This TwoClientPreferencesSyncTestWithSelfNotifications test case is
> > flaky.
> > 
> > TBR=mastiz@chromium.org
> > 
> > Bug: 1012688
> > Change-Id: I33f1956523be55f3f77db0560aac4c3de6721341
> > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1859635
> > Reviewed-by: Lei Zhang <thestig@chromium.org>
> > Reviewed-by: Mikel Astiz <mastiz@chromium.org>
> > Commit-Queue: Lei Zhang <thestig@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#705625}
> 
> Bug: 1012688
> Change-Id: Idb70d277042bcb98a94130da3f2bab59ffaf0d20
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1898651
> Reviewed-by: Lei Zhang <thestig@chromium.org>
> Commit-Queue: Mikel Astiz <mastiz@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#712514}

TBR=thestig@chromium.org,mastiz@chromium.org

Change-Id: I9a7cd1cf5079a164285d7f6242c1ae310f7d13f3
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1012688
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1899465Reviewed-by: Mikel Astiz <mastiz@chromium.org>
Commit-Queue: Mikel Astiz <mastiz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#712570}

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

@@ -190,10 +190,8 @@ class TwoClientPreferencesSyncTestWithSelfNotifications : public SyncTest {
   DISALLOW_COPY_AND_ASSIGN(TwoClientPreferencesSyncTestWithSelfNotifications);
 };
 
-// Flaky. https://crbug.com/1012688
-// This was E2E_ENABLED(ShouldKeepLocalDataOnTypeMismatch).
 IN_PROC_BROWSER_TEST_F(TwoClientPreferencesSyncTestWithSelfNotifications,
-                       DISABLED_ShouldKeepLocalDataOnTypeMismatch) {
+                       E2E_ENABLED(ShouldKeepLocalDataOnTypeMismatch)) {
   ResetSyncForPrimaryAccount();
   ASSERT_TRUE(SetupClients()) << "SetupClients() failed.";