fix regress tests for PostgreSQL 17

Author: okbob

expected/README

@@ -1,4 +1,5 @@
 plpgsql_check_passive.out			PostgreSQL 14, 15, 16
 plpgsql_check_passive_1.out			PostgreSQL 12, 13
 plpgsql_check_active_1.out			PostgreSQL 12, 13
-plpgsql_check_active.out			PostgreSQL 14, 15, 16, 17
+plpgsql_check_active_2.out			PostgreSQL 14, 15, 16
+plpgsql_check_active.out			PostgreSQL 17

expected/plpgsql_check_active.out

@@ -3011,7 +3011,8 @@ end;
 $$ language plpgsql;
 -- should to fail
 select testseq();
-ERROR:  "test_table" is not a sequence
+ERROR:  cannot open relation "test_table"
+DETAIL:  This operation is not supported for tables.
 CONTEXT:  SQL statement "SELECT nextval('test_table')"
 PL/pgSQL function testseq() line 3 at PERFORM
 select * from plpgsql_check_function('testseq()', fatal_errors := false);