feat(expressive): Update magnification mode images to expressive style

This is not flagged because these images look fine when the expressive
flag is on or off, so using one source of truth is simpler to maintain.

Also removes tablet assets since the new images are form factor
agnostic.

Fix: 400519514
Test: observe new images; see screenshots in bug
Flag: EXEMPT image assets only
Change-Id: I35773421abbd5aa4b32a8ef45ecdc8c04748caf1