Don't explicitly wait for starting-window during tests with shell-transitions

Starting-window is part of sync-set when using shell-transitions,
so don't wait for it separately in waitForAnimationsToComplete because
it will just time-out.

Bug: 183993924
Test: atest WindowUntrustedTouchTests
Change-Id: I4788148dab3e6b957a7d37dee01587b904d46e48