re-add the peer grading tab for students

lms/templates/courseware/course_navigation.html

@@ -17,7 +17,6 @@ def url_class(is_active):
   <div class="inner-wrapper">
     <ol class="course-tabs">
       % for tab in get_course_tabs(user, course, active_page):
-        % if tab.name != "Grading Panel" or staff_access:
         <li>
            <a href="${tab.link | h}" class="${url_class(tab.is_active)}">
                ${tab.name | h}
@@ -29,7 +28,6 @@ def url_class(is_active):
                %endif
            </a>
         </li>
-        % endif
       % endfor
     <%block name="extratabs" />
         % if masquerade is not UNDEFINED: