MDL-59970 competencies: performance

Remove useless get_records call in get_least_proficient_competencies_for_course function.
On big sites this would cause huge memory usage.

competency/classes/user_competency_course.php

@@ -282,7 +282,6 @@ class user_competency_course extends persistent {
               ORDER BY p.timesproficient ASC, c.id DESC';
 
         $results = $DB->get_records_sql($sql, $params, $skip, $limit);
-        $a = $DB->get_records_sql('SELECT * from {' . self::TABLE . '}');
 
         $comps = array();
         foreach ($results as $r) {