Normative cite of LANG-SUBTAG-REGISTRY.

Co-authored-by: Ted Thibodeau Jr <tthibodeau@openlinksw.com>

Author: gkellogg

spec/index.html

@@ -619,7 +619,7 @@ <h3>Grammar</h3>
           match the pattern for <a href="#grammar-production-LANGTAG">LANGTAG</a>,
           though neither "<code class="grammar-literal">prefix</code>"
           nor "<code class="grammar-literal">base</code>"
-          are <a data-cite="?LANG-SUBTAG-REGISTRY#">registered language subtags</a> [[LANG-SUBTAG-REGISTRY]].
+          are <a data-cite="LANG-SUBTAG-REGISTRY#">registered language subtags</a> [[LANG-SUBTAG-REGISTRY]].
           This specification does not define whether a quoted literal followed by
           either of these tokens (e.g., <code>"Z"@base</code>) is in the TriG language.
         </li>