fix python syntax in template for adding google analytics

lms/templates/main.html

@@ -20,7 +20,7 @@
   <![endif]-->
   <meta name="path_prefix" content="${MITX_ROOT_URL}">
 
-  % if course == false:
+  % if not course:
     <script type="text/javascript"> 
 
       var _gaq = _gaq || [];