remove group notation from outline (#11094)

Author: keithamus

css-ui-4/Overview.bs

@@ -280,7 +280,7 @@ Outline properties</h2>
 
 	<pre class="propdef shorthand">
 	Name: outline
-	Value: [ <<'outline-width'>> || <<'outline-style'>> || <<'outline-color'>> ]
+	Value: <<'outline-width'>> || <<'outline-style'>> || <<'outline-color'>>
 	Applies to: all elements
 	Inherited: no
 	Percentages: N/A