Mention enahncements in release notes (#11006)

all/src/main/templates/release-notes.html

             enhancements. Below is a list of the most notable changes:</p>
 
         <ul>
+
+        <li><tt>Upload</tt> component now supports <tt>accept</tt> attribute.</li>
+        <li><tt>SerializablePredicate</tt> has new helper APIs.</li>
+
         </ul>
 
         </p>