[css-ui-4][editorial] Let outline-color refer to border-top-color values (#12993)

Author: SebastianZ

css-ui-4/Overview.bs

@@ -476,7 +476,7 @@ Outline Colors: the 'outline-color' property</h3>
 
 	<pre class="propdef">
 	Name: outline-color
-	Value: auto | <<color>> | <<image-1D>>
+	Value: auto | <<'border-top-color'>>
 	Initial: auto
 	Applies to: all elements
 	Inherited: no
@@ -486,7 +486,7 @@ Outline Colors: the 'outline-color' property</h3>
 	</pre>
 
 	The 'outline-color' property
-	accepts all values of <'border-color'>,
+	accepts all values of <<'border-top-color'>>,
 	as well as the following keywords:
 
 	<dl dfn-type=value dfn-for=outline-color>
@@ -2856,7 +2856,8 @@ Changes from the <a href="https://www.w3.org/TR/2021/WD-css-ui-4-20210316/">16 M
 			(Support for the broader <<image>> type remains allowed but optional.)
 
 		<li>
-			Added <<image-1D>> as value for the 'outline-color' property.
+			Replaced the <<color>> value of the 'outline-color' property by <<'border-top-color'>>,
+			so that new values like <<image-1D>> also apply to it.
 
 		<li>
 			Retired the <code>invert</code> value of 'outline-color'.