Don't leave regress_test_role_super lying around.

Fixes an oversight in commit fc6d1006.

Noted by Tom Lane.

src/test/regress/expected/foreign_data.out

@@ -208,6 +208,7 @@ DETAIL:  owner of foreign-data wrapper foo
 SET ROLE regress_test_role_super;
 DROP FOREIGN DATA WRAPPER foo;
 RESET ROLE;
+DROP ROLE regress_test_role_super;
 \dew+
                                             List of foreign-data wrappers
     Name    |       Owner       | Handler |        Validator         | Access privileges | FDW Options | Description 

src/test/regress/sql/foreign_data.sql

@@ -97,6 +97,7 @@ DROP ROLE regress_test_role_super;                          -- ERROR
 SET ROLE regress_test_role_super;
 DROP FOREIGN DATA WRAPPER foo;
 RESET ROLE;
+DROP ROLE regress_test_role_super;
 \dew+
 
 CREATE FOREIGN DATA WRAPPER foo;