Remove waitForWindowUpdate from UI tests

This call was required originally to prevent flakiness in the UI tests. But since ag/19817573 added retry with wait for all UI tests, it is not required anymore.

Bug: 264537784
Test: atest SafetyCenterActivityTest --iterations 10
Change-Id: Idc5f683e45143ba3098422a3c426bbee21f0e43b