Add "updateable-rec" class to SODT.

This marks adds "Future updates to this Recommendation may incorporate new features.", Where, "new features" is a link to the process document: https://www.w3.org/2023/Process-20231103/#allow-new-features.

For a recommendation to be updatable, it MUST include this reference, The SODT template doesn't really allow changing the wording of this paragraph.

Author: gkellogg

spec/index.html

@@ -138,7 +138,7 @@
     performed.</p>
 </section>
 
-<section id="sotd">
+<section id="sotd" class="updateable-rec">
   <p>This document describes the <a>RDFC-1.0</a> algorithm for canonicalizing
     RDF datasets, which was the input from the
     <a href="https://www.w3.org/community/credentials/">W3C Credentials Community Group</a>