Screen Capture: Update RadioButtonGroup button colors

The screen capture component UX spec was recently updated to align
closer to M3 guidelines. This updates the button colors to match the
UX spec.

Bug: 412722889, 412722410
Test: Screenshot tests
Flag: com.android.systemui.desktop_screen_capture
Change-Id: Ic1ce48701525e43161c8ecbd503794e075541db8