Disable UKMTestCase testConsentAddedButNoSync

TBR=jlebel@chromium.org

Bug: 989726
Change-Id: I391c68caa6fb7804a6162f1fc78343e192b3ba0f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1728341Reviewed-by: Mike Dougherty <michaeldo@chromium.org>
Commit-Queue: Mike Dougherty <michaeldo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#682953}

ios/chrome/browser/metrics/ukm_egtest.mm

@@ -317,7 +317,8 @@ void SignOut() {
 }
 
 // Make sure that providing metrics consent doesn't enable UKM w/o sync.
-- (void)testConsentAddedButNoSync {
+// TODO(crbug.com/989726): Re-enable this crashing test.
+- (void)DISABLED_testConsentAddedButNoSync {
   SignOut();
   UpdateMetricsConsent(false);
   AssertUKMEnabled(false);