feat(expressive): Update flash notifications image to expressive style

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

Fix: 400715600
Test: observe new images; see screenshots in bug
Flag: EXEMPT image assets only
Change-Id: Id8d88946e05a52373c493b047c88b7ad1e11007f