disambiguate 'none'

Author: svgeesus

css-fonts-4/Overview.bs

@@ -3634,7 +3634,7 @@ this feature is on by default.</dd>
 <p id=rlig-unaffected"><em>Required</em> ligatures,
 needed for correctly rendering complex scripts,
 are not affected by the settings above,
-including 'none'
+including <span title="normal!!font-variant-ligatures">'normal'</span>
 (OpenType feature: <span class="tag">rlig</span>).</p>
 
 <h3 id="font-variant-position-prop">