Remove submission buttons from aria-live region

added a new aria-live region and added problem html into that.
Removed submission buttons out of the aria-live div scope.

TNL-1699

lms/templates/problem.html

@@ -7,9 +7,10 @@
 
 <div class="problem-progress"></div>
 
-<div class="problem" aria-live="polite" aria-relevant="all">
-  ${ problem['html'] }
-
+<div class="problem">
+    <div aria-live="polite">
+        ${ problem['html'] }
+    </div>
   <div class="action">
     <input type="hidden" name="problem_id" value="${ problem['name'] }" />
 
@@ -26,7 +27,7 @@
     <button class="show"><span class="show-label">${_('Show Answer')}</span> </button>
     % endif
     % if attempts_allowed :
-    <div class="submission_feedback">
+    <div class="submission_feedback" aria-live="polite">
       ${_("You have used {num_used} of {num_total} submissions").format(num_used=attempts_used, num_total=attempts_allowed)}
     </div>
     % endif