[ios] Disable flaky test FirstRunTestCase testDismissFirstRun.

TBR=jlebel@chromium.org

Bug: 1061085
Change-Id: I0ec1b61971ac6b9723b8f6eab2425b97aa84c5c0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2100717Reviewed-by: edchin <edchin@chromium.org>
Commit-Queue: edchin <edchin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#749774}

ios/chrome/browser/ui/first_run/first_run_egtest.mm

@@ -119,7 +119,8 @@ id<GREYMatcher> SkipSigninButton() {
 }
 
 // Dismisses the first run screens.
-- (void)testDismissFirstRun {
+// TODO(crbug.com/1061085): This test is flaky and has timeout.
+- (void)FLAKY_testDismissFirstRun {
   [FirstRunAppInterface showFirstRunUI];
 
   [[EarlGrey selectElementWithMatcher:FirstRunOptInAcceptButton()]