remove unneeded aria live elements, phetsims/chipper#637

circuit-construction-kit-black-box-study_en.html

@@ -17,10 +17,7 @@
 <!-- a11y - aria-live attribute is used to send alerts and status updates to screen readers, otherwise invisible -->
 <div id='aria-live-elements'
      style="position: absolute; left: 0px; top: 0px; width: 0px; height: 0px; clip: rect(0px 0px 0px 0px); pointer-events: none;">
-  <p id="assertive" aria-live="assertive"></p>
   <p id="polite" aria-live="polite"></p>
-  <p id="assertive-alert" aria-live="assertive" role="alert"></p>
-  <p id="polite-status" aria-live="polite" role="status"></p>
 </div>
 
 <script type="text/javascript">