[css-view-transitions-2] Revisit the -ua- types fix to make parsing invalid (#14111)

* Make parsing fail on invalid types

* Also fix header

Author: noamr

css-view-transitions-2/Overview.bs

@@ -2026,7 +2026,7 @@ The [=@view-transition/types=] descriptor
 	<pre class='descdef'>
 	Name: types
 	For: @view-transition
-	Value: none | <<custom-ident>>+
+	Value: none | <<view-transition-type>>+
 	Initial: none
 	</pre>
 
@@ -2037,11 +2037,12 @@ The [=@view-transition/types=] descriptor
 		: <dfn>none</dfn>
 		:: No transition types are set.
 
-		: <dfn><<custom-ident>>+</dfn>
+		: <dfn><<view-transition-type>>+</dfn>
 		:: Sets the [=ViewTransition/active types=] for the transition to the specified custom identifiers.
-			 The <<custom-ident>> `none`, as well as any <<custom-ident>> starting with `-ua-`, are ignored.
 	</dl>
 
+	where <<view-transition-type>> is any <<custom-ident>> other than `none`, and not starting with the string "-ua-".
+
 	Note: the [=@view-transition/types=] descriptor only applies to the {{Document}} in which it is defined.
 	The author is responsible for using their chosen set of types in both documents.