feat(note): use gray tokens

Author: thetaPC

core/src/components/note/note.md.vars.scss

@@ -4,7 +4,7 @@
 // --------------------------------------------------
 
 /// @prop - Text color of the note
-$note-md-color: $text-color-step-400;
+$note-md-color: var(--ion-color-gray-600);
 
 /// @prop - Font size of the note
 $note-md-font-size: dynamic-font(14px);