Add bottom padding to 'Choose a new lock screen'

* Add 24dp padding

Before: https://screenshot.googleplex.com/64sTaMhwqMKQ4CE
After: https://screenshot.googleplex.com/As33LmkLXG7duV5

Bug: 192541032
Test: manual testing (see screenshots)
Change-Id: I4e29e4f776e7be1c42301c39c4844d7ee948eaaa
1 file changed