[iOS] Re-enable test on CQ

Test was marked as flaky on July 14 but it doesn't do anything
differently from that the other tests in the same suite. Since this test
case involves tapping on a JS form field and bringing up the keyboard, I
think the flakiness of this test depends a lot on the device /
simulator. Re-enabling to see if it's less flaky on better CQ
environment.

Bug: 431975187
Change-Id: I004c6fcb5f57fd32dae88a2612e90bc46064e896
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6891831
Reviewed-by: Alexis Hétu <sugoi@chromium.org>
Commit-Queue: Ginny Huang <ginnyhuang@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1507761}