Fixes dark-text-dark-background on A11yMenu grid items.

Screenshots:
- Light mode: https://screenshot.googleplex.com/BBjAK3rW3QRaZnj.png
- Dark mode: https://screenshot.googleplex.com/83x8x4VEuc2spXM.png

Flag: RESOURCES_ONLY
Test: launch menu in light & dark mode, observe text is
      white-on-black or black-on-white.
Change-Id: I545cdb7acbcba99bd719dc376ab48482fc022a88