[css-view-transitions-1] Don't define auto in the syntax

This is inconsistent with how other specs define custom ident restrictions.

Author: nt1m

css-view-transitions-1/Overview.bs

@@ -511,7 +511,7 @@ urlPrefix: https://wicg.github.io/navigation-api/; type: interface;
 
 	<pre class=propdef>
 	Name: view-transition-name
-	Value: none | auto | <<custom-ident>>
+	Value: none | <<custom-ident>>
 	Initial: none
 	Inherited: no
 	Percentages: n/a
@@ -534,9 +534,6 @@ urlPrefix: https://wicg.github.io/navigation-api/; type: interface;
 		: <dfn>none</dfn>
 		:: The [=/element=] will not participate independently in a view transition.
 
-		: <dfn>auto</dfn>
-		:: This should be treated as an invalid value, despite being a valid <<custom-ident>>. The property value remains unchanged.
-
 		: <dfn><<custom-ident>></dfn>
 		:: The [=/element=] participates independently in a view transition--
 			as either an old or new [=/element=]--