tonePrefersLightForeground

People prefer white foregrounds on ~T60-70. Observed over time, and also by Andrew Somers during research for APCA.

T60 used as to create the smallest discontinuity possible when skipping down to T49 in order to ensure light foregrounds.

Since tertiaryContainer in dark monochrome scheme requires a tone of 60, it should not be adjusted. Therefore, 60 is excluded here.