Fix courses link in LMS header when not logged in

lms/templates/navigation.html

@@ -81,7 +81,7 @@ site_status_msg = get_site_status_msg(course_id)
         <a href="${marketing_link('HOW_IT_WORKS')}">How it Works</a>
       </li>
       <li class="nav-global-02">
-        <a href="marketing_link('COURSES')}">Courses</a>
+        <a href="${marketing_link('COURSES')}">Courses</a>
       </li>
       <li class="nav-global-03">
         <a href="${marketing_link('SCHOOLS')}">Schools</a>