Add elevation to BottomSheet of BottomActionBar

Before: https://screenshot.googleplex.com/Jp3qRtDCpQD.png
After: https://screenshot.googleplex.com/dxJEBS5vtCf.png

Test: Manually
Bug: 151892004
Change-Id: I430d92fe7e9734592609cda70a89864f08fdc570
1 file changed