Make testSplitscreenPortraitAppOrientationRequests pass to unblock release

Work around to unblock the release for failing test
ActivityManagerAppConfigurationTests#testSplitscreenPortraitAppOrientationRequests
which shouldn't be failing since home stack shouldn't be visible. We need
to dig deeper to see why it is failing.
NOTE: Not failing on current master...

Bug: 110159357
Test: atest ActivityManagerAppConfigurationTests#testSplitscreenPortraitAppOrientationRequests
Change-Id: I69423eef3661133b2a032a166745157b3e344751