Update install app icon colors to spec:

The + in the icon is onSurface.
Everything else within the circle is material_color_surface_container_lowest.

spec: https://docs.google.com/presentation/d/1_f2nAcmZMywF0D1-9fJv1slUQVerIpJ0b1uUmZDpKXo/edit?resourcekey=0-nxjnkIp8z-ECp8angeQJZg#slide=id.g239ecda44ed_0_18

bug: 340307977
Test:
before: https://screenshot.googleplex.com/Bss6VHDt7JfjsEU
after: https://screenshot.googleplex.com/5qxqQ6segow2Nxh
Flag: None
Change-Id: I300e8513d15e428338cb1e20f65fbe3a0b62bc35