comma is necessary between url and predefined "fallback" cursor

fixes w3c#13001

Author: tyrasd

css-ui-3/Overview.bs

@@ -921,7 +921,7 @@ While the content is being scrolled, implementations may adjust their rendering
 
 <pre class="propdef">
 Name: cursor
-Value: <<cursor-image>>#? <<cursor-predefined>>
+Value: <<cursor-image>>#? , <<cursor-predefined>>
 Initial: auto
 Applies to: all elements
 Inherited: yes

css-ui-4/Overview.bs

@@ -720,7 +720,7 @@ Styling the Cursor: the 'cursor' property</h4>
 
 	<pre class="propdef">
 	Name: cursor
-	Value: <<cursor-image>>#? <<cursor-predefined>>
+	Value: <<cursor-image>>#? , <<cursor-predefined>>
 	Initial: auto
 	Applies to: all elements
 	Inherited: yes