Improve usability showing disabled lines in forms

* Use gray-3 instead of gray-2 for text-color-weak in "light" theme

public/sass/_variables.light.scss

@@ -56,7 +56,7 @@ $page-bg: $gray-7;
 $body-color: $gray-1;
 $text-color: $gray-1;
 $text-color-strong: $dark-2;
-$text-color-weak: $gray-2;
+$text-color-weak: $gray-3;
 $text-color-faint: $gray-4;
 $text-color-emphasis: $dark-5;