Update private space divider thickness and padding per spec.

Thickness (height) is 2dp.
Padding above and below the divider is 32dp.

bug: 340307977
test manually:
before: https://drive.google.com/file/d/1H364XUILz3gTLOENQL5zQBOELcza7YBk/view?usp=sharing
after: https://drive.google.com/file/d/1HCsnj2s9TwlzIjKL1aHbBqO15nkPoOLj/view?usp=sharing
after vertical padding: https://drive.google.com/file/d/1HS1SFVj9RfvuxHPGyk0PH5dGQum3spqe/view?usp=sharing
Flag: None

Change-Id: I64e9a228e9095449c4ef5f7680d92d234ab96f9f