Fix typo

Thanks to Thomas Hoppe for reporting it

spec/latest/core/index.html

@@ -309,7 +309,7 @@ <h3>Adding Affordances to Representations</h3>
     </pre>
 
     <p>In the example above, a property identified with the URL
-      <code>http://api.example.com/vocab#comments</code> is be defined to be
+      <code>http://api.example.com/vocab#comments</code> is defined to be
       of the type <i>Link</i>. This is enough information for a client
       understanding Hydra to know that the value of the
       <code>comments</code> property in the following example is intended