update polling container to aside element

bigbluebutton-html5/imports/ui/components/polling/component.jsx

@@ -304,7 +304,7 @@ class Polling extends Component {
         <Styled.PollingContainer
           autoWidth={stackOptions}
           data-test="pollingContainer"
-          role="alert"
+          role="complementary"
           ref={el => this.pollingContainer = el}
           tabIndex={-1}
         >

bigbluebutton-html5/imports/ui/components/polling/styles.js

@@ -144,7 +144,7 @@ const QText = styled.div`
   padding-right: ${smPaddingX};
 `;
 
-const PollingContainer = styled.div`
+const PollingContainer = styled.aside`
   pointer-events:auto;
   min-width: ${pollWidth};
   position: absolute;