Make the setting description more descriptive (#655)

Author: mdjnelson

lang/en/customcert.php

@@ -204,7 +204,7 @@
 $string['replacetemplate'] = 'Replace';
 $string['requiredtimenotmet'] = 'You must spend at least a minimum of {$a->requiredtime} minutes in the course before you can access this certificate.';
 $string['returncourse'] = 'Return to course button';
-$string['returncourse_desc'] = 'Display a "return to course" button';
+$string['returncourse_desc'] = 'Display a "Return to course" button on the view certificate page.';
 $string['returncourselabel'] = 'Return to course menu';
 $string['rightmargin'] = 'Right margin';
 $string['rightmargin_help'] = 'This is the right margin of the certificate PDF in mm.';