Fix inaccurate instructions around import

cms/templates/import.html

@@ -21,14 +21,14 @@
       <div class="description">
         <p><strong>Importing a new course will delete all content currently associated with your course
         and replace it with the contents of the uploaded file.</strong></p>
-        <p>File uploads must be gzipped tar files (.tar.gz or .tgz) containing, at a minimum, a <code>course.xml</code> file.</p>
+        <p>File uploads must be gzipped tar files (.tar.gz) containing, at a minimum, a <code>course.xml</code> file.</p>
         <p>Please note that if your course has any problems with auto-generated <code>url_name</code> nodes,
         re-importing your course could cause the loss of student data associated with those problems.</p>
       </div>
       <form action="${reverse('import_course', kwargs=dict(org=context_course.location.org, course=context_course.location.course, name=context_course.location.name))}" method="post" enctype="multipart/form-data" class="import-form">
         <h2>Course to import:</h2>
         <p class="error-block"></p>
-        <a href="#" class="choose-file-button">Choose File</a>        
+        <a href="#" class="choose-file-button">Choose File</a>
         <p class="file-name-block"><span class="file-name"></span><a href="#" class="choose-file-button-inline">change</a></p>
         <input type="file" name="course-data" class="file-input">
         <input type="submit" value="Replace my course with the one above" class="submit-button">
@@ -45,13 +45,13 @@
 <%block name="jsextra">
 <script>
 (function() {
-    
+
 var bar = $('.progress-bar');
 var fill = $('.progress-fill');
 var percent = $('.percent');
 var status = $('#status');
 var submitBtn = $('.submit-button');
-   
+
 $('form').ajaxForm({
     beforeSend: function() {
         status.empty();
@@ -76,7 +76,7 @@ $('form').ajaxForm({
         submitBtn.show();
         bar.hide();
     }
-  }); 
-})();       
+  });
+})();
 </script>
 </%block>
\ No newline at end of file