Fix GROUP BY in show_departments() for PostgreSQL strictness

PostgreSQL requires all non-aggregated columns in GROUP BY clause,
unlike MySQL which allows functional dependency. Add dept_name and
manager to GROUP BY.

Author: renecannao

postgresql/objects.sql

@@ -168,7 +168,7 @@ BEGIN
         dept_no, dept_name, manager, COUNT(*)
     FROM v_full_departments
         INNER JOIN department_people USING (dept_no)
-    GROUP BY dept_no;
+    GROUP BY dept_no, dept_name, manager;
 
     DROP TABLE department_max_date;
     DROP TABLE department_people;