Update DART SASS dependency

[cderv]

We use 1.70.0

quarto-cli/configuration

Line 15 in 7f8cfd0

export DARTSASS=1.70.0

The latest one is 1.85.1
https://github.com/sass/dart-sass/releases/tag/1.85.1

SASS docs are for 1.85.1, so the further we keep them apart, the more difficult it for users will be to know which works or not.

Example: a user tried to follow deprecation recommendation and use color.channel() from 1.79.0