[css-color-4] Consistently distinguished opacity from alpha, #8311

Author: svgeesus

css-color-4/Overview.bs

@@ -649,10 +649,8 @@ Transparency: the 'opacity' property</h3>
 		inline-opacity-float-child.html
 	</wpt>
 
-	Opacity in CSS is typically represented using the <<opacity-value>> syntax,
-	for example in the 'opacity' property
-	or as the [=alpha component=] in a [=color function=],
-	using the <<alpha-value>> syntax.
+	Opacity in CSS is represented using the <<opacity-value>> syntax,
+	for example in the 'opacity' property.
 	Represented as a <<number>>, the useful range of the value is ''0''
 	(representing full transparency)
 	to ''1''