Fix flaky passengerShowImeNotAffectDriver()

The test was flaky because sometimes the app window on the passenger
display stayed black forever after the test activity was launched on
the passenger display.
This CL fixed by removing problematic and unnecessary window animation.

Bug: 350562427
Test: atest com.android.server.inputmethod.multisessiontest.ConcurrentMultiUserTest --iterations 100
Flag: TEST_ONLY
Change-Id: Ieec9d815a85dfd218cf51f5960cb4172ba537af1
1 file changed