Better not set §B as non-normative (minor editorial)

At the moment §B declares itself as non-normative, and this is, sort of, "inherited" by subsections unless stated otherwise. Ie, §B.1 and §B.2 may be considered as non-normative, which is not the intention. Better leave §B to normative (the default) and §B.3 explicitly declares itself as non-normative.

Just to avoid misunderstandings...

index.html

@@ -5352,7 +5352,7 @@ <h3>Fitness for Purpose</h3>
       </section>
     </section>
 
-    <section class="appendix informative">
+    <section class="appendix">
       <h2>Contexts, Vocabularies, Types, and Credential Schemas</h2>
 
       <section class="normative">