Core: Fixed gray-light so meets colour contrast against white backgrounds

Fixes #5599

This colour is also associated with disabled fields which had contrast issues as well (so fixes numerous contrast issues all at once).
OK, I got confused because I remember remapping those before https://github.com/wet-boew/wet-boew/blob/v4-sass-color-variables/src/_variables.scss
Guess I should finish that work eventually :wink: