repository MDL-15404 change text description for allowing teacher/user to add repository

lang/en_utf8/repository.php

@@ -37,8 +37,8 @@ $string['download'] = 'Download';
 $string['downloadsucc'] = 'The file has been downloaded successfully';
 $string['editrepositoryinstance'] = 'Edit repository instance';
 $string['emptytype'] = 'Cannot create repository type: type name is empty';
-$string['enablecourseinstances'] = 'Enable course repositories';
-$string['enableuserinstances'] = 'Enable user repositories';
+$string['enablecourseinstances'] = 'Allow teachers to add a repository instance into the file picker';
+$string['enableuserinstances'] = 'Allow users to add a repository instance into the file picker';
 $string['error'] = 'An unknown error occurred!';
 $string['existingrepository'] = 'This repository already exists';
 $string['filename'] = 'Filename';