Move click handler from XML to ViewModel (1/2)

This CL moves the click handler that is called when the "Got it" button
of the (empty) PeopleSpaceActivity is clicked from XML to the
PeopleViewModel. I missed it when I refactored this Activity in
ag/19268008.

Bug: 238993727
Test: Manual
Change-Id: I7451589267aac5b07d0c979d5dde606e37915220