[css-ui-3][editorial] Let 'background-' and 'border-' properties refer to CSS Backgrounds 3 instead of CSS 2

Author: SebastianZ

css-ui-3/Overview.bs

@@ -59,13 +59,6 @@ spec:css2; type:property
 	text:width
 	text:height
 	text:left
-	text:border-bottom-width
-	text:border-left-width
-	text:border-right-width
-	text:border-top-width
-	text:border-style
-	text:border-width
-	text:background-image
 	text:min-width
 	text:min-height
 	text:max-width
@@ -80,7 +73,15 @@ spec:css2; type:property
 	text:padding-top
 	text:visibility
 spec:css-backgrounds-3;
-	type:property; text:border-radius;
+	type:property;
+		text:background-image
+		text:border-bottom-width
+		text:border-left-width
+		text:border-right-width
+		text:border-top-width
+		text:border-style
+		text:border-width
+		text:border-radius;
 	type:type; text:<line-width>
 	type:value; for:border-style; text:none
 </pre>
@@ -1789,6 +1790,7 @@ Changes from the <a href="https://www.w3.org/TR/2018/REC-css-ui-3-20180621/">21
 	<li>Let computed value of 'outline-width' be [=snapped as a border width=]
 	<li>Added Web Platform Tests coverage
 	<li>Split privacy and security considerations into separate sections
+	<li>Let <css>background-*</css> and <css>border-*</css> properties refer to [[CSS-BACKGROUNDS-3]] instead of [[CSS2]]
 	<li>Editorial improvements
 </ul>