MDL-30583 Navigation : fixed string.

lang/en/admin.php

@@ -694,7 +694,7 @@
 $string['navlinkcoursesections'] = 'Link course sections';
 $string['navlinkcoursesections_help'] = 'If enabled course sections will be shown as links within the navigation.';
 $string['navshowfrontpagemods'] = 'Show front page activities in the navigation';
-$string['navshowfrontpagemods_help'] = 'If enabled front page activities will be shown on the navigation under site pages.';
+$string['navshowfrontpagemods_help'] = 'If enabled, front page activities will be shown on the navigation under site pages.';
 $string['navshowallcourses'] = 'Show all courses';
 $string['navshowcategories'] = 'Show course categories';
 $string['neverdeleteruns'] = 'Never delete runs';