ExpandHelper and ExpandHelperTest now use AndroidX / AnimatorTestRule am: 86e318e404 am: 65998eb6b7

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/24225905

Change-Id: I696ff9f0567ce1480f7a53c5bf68272b2d022aad
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>