studio - further resolved bug with .header CSS inheritance and problem editor menu UI

cms/templates/widgets/problem-edit.html

@@ -4,8 +4,8 @@
         %if markdown != '' or data == '<problem>\n</problem>\n':
         <div class="editor-bar">
             <ul class="format-buttons">
-                <li><a href="#" class="header-button" data-tooltip="Header"><span
-                        class="problem-editor-icon header"></span></a></li>
+                <li><a href="#" class="header-button" data-tooltip="Heading 1"><span
+                        class="problem-editor-icon heading1"></span></a></li>
                 <li><a href="#" class="multiple-choice-button" data-tooltip="Multiple Choice"><span
                         class="problem-editor-icon multiple-choice"></span></a></li>
                 <li><a href="#" class="checks-button" data-tooltip="Check Multiple"><span

common/lib/xmodule/xmodule/css/problem/edit.scss

@@ -107,11 +107,9 @@
   background: url(../img/problem-editor-icons.png) no-repeat;
 }
 
-.problem-editor-icon.header {
+.problem-editor-icon.heading1 {
   width: 18px;
   background-position: -265px 0;
-  border: none;
-  padding: 0;
 }
 
 .problem-editor-icon.multiple-choice {