Polish ActivityEmbedding Shell animation when open a split pair

Before, we are checking TransitionInfo.isIndependent, which is true when
the parent is TRANSIT_CHANGE. However, we already animate the change
parent here, so we should skip the child for such case.

Bug: 207070762
Test: manually verify the animation
Change-Id: I3d1342ef27c97b2c8bb7270975f1f089c4462d5b