[css-navigation-1] Allow navigation-param() without extra parentheses around it. (#13159)

Author: dbaron

css-navigation-1/Overview.bs

@@ -456,7 +456,7 @@ by matching the relevant parts of the navigation URL to the link URL.
    the match with the link's target.
    */
 .movie-container:has(> .movie-title:link-to(
-  --movie-details with (navigation-param(id)))) {
+  --movie-details with navigation-param(id))) {
 
   view-transition-name: movie-container;
 
@@ -479,21 +479,18 @@ and the pseudo-class matches any element where:
 <pre class="prod def" dfn-type="type" nohighlight>
 <dfn><<link-condition>></dfn> = <<link-condition-base>> [ with <<navigation-param-expression>> ]?
 <dfn><<link-condition-base>></dfn> = <<navigation-location>>
-<dfn><<navigation-param-expression>></dfn> = ( [ <<navigation-param-and>> |
-                                    <<navigation-param-or>> |
-                                    <<navigation-param>> ] )
+<dfn><<navigation-param-expression>></dfn> = ( <<navigation-param-and>> ) |
+                                ( <<navigation-param-or>> ) |
+                                <<navigation-param>>
 <dfn><<navigation-param-and>></dfn> = <<navigation-param-expression>>
                          [ "and" <<navigation-param-expression>> ]*
 <dfn><<navigation-param-or>></dfn> = <<navigation-param-expression>>
                         [ "or" <<navigation-param-expression>> ]*
 <dfn><<navigation-param>></dfn> = <<navigation-param-key-value>> | <<navigation-param-function>>
-<dfn><<navigation-param-key-value>></dfn> = <<ident>> : <<string>>
+<dfn><<navigation-param-key-value>></dfn> = ( <<ident>> : <<string>> )
 <dfn><<navigation-param-function>></dfn> = navigation-param( <<ident>> )
 </pre>
 
-ISSUE: This grammar should be restructured so that
-it doesn't require parentheses around a lone <<navigation-param-function>>.
-
 A <<link-condition>> matches the target of the link when both:
 * the <<link-condition-base>> matches the target of the link, and
 * the <<navigation-param-expression>> matches the target of the link,