Fix StudentService#passedPrerequisitesForCourse document

     *

     * @param studentId

     * @param courseId

     * @return true if the student has any course score record that is passed (>=60 or PASS), which means he has passed the course.

     * @return true if the student has passed the course's prerequisites (>=60 or PASS).

     */

    boolean passedPrerequisitesForCourse(int studentId, String courseId);