Fix typos in regression test comments.

Author: Etsuro Fujita

src/test/regress/expected/partition_join.out

@@ -1959,7 +1959,7 @@ SELECT t1.a, t1.c, t2.b, t2.c FROM prt1_n t1 JOIN prt2_n t2 ON (t1.c = t2.c) JOI
 (16 rows)
 
 -- partitionwise join can not be applied for a join between list and range
--- partitioned table
+-- partitioned tables
 EXPLAIN (COSTS OFF)
 SELECT t1.a, t1.c, t2.b, t2.c FROM prt1_n t1 FULL JOIN prt1 t2 ON (t1.c = t2.c);
                   QUERY PLAN                  
@@ -1976,7 +1976,7 @@ SELECT t1.a, t1.c, t2.b, t2.c FROM prt1_n t1 FULL JOIN prt1 t2 ON (t1.c = t2.c);
                ->  Seq Scan on prt1_n_p2 t1_1
 (10 rows)
 
--- partitionwise join can not be applied if only one of joining table has
+-- partitionwise join can not be applied if only one of joining tables has
 -- default partition
 ALTER TABLE prt2 DETACH PARTITION prt2_p3;
 ALTER TABLE prt2 ATTACH PARTITION prt2_p3 FOR VALUES FROM (500) TO (600);

src/test/regress/sql/partition_join.sql

@@ -423,11 +423,11 @@ EXPLAIN (COSTS OFF)
 SELECT t1.a, t1.c, t2.b, t2.c FROM prt1_n t1 JOIN prt2_n t2 ON (t1.c = t2.c) JOIN plt1 t3 ON (t1.c = t3.c);
 
 -- partitionwise join can not be applied for a join between list and range
--- partitioned table
+-- partitioned tables
 EXPLAIN (COSTS OFF)
 SELECT t1.a, t1.c, t2.b, t2.c FROM prt1_n t1 FULL JOIN prt1 t2 ON (t1.c = t2.c);
 
--- partitionwise join can not be applied if only one of joining table has
+-- partitionwise join can not be applied if only one of joining tables has
 -- default partition
 ALTER TABLE prt2 DETACH PARTITION prt2_p3;
 ALTER TABLE prt2 ATTACH PARTITION prt2_p3 FOR VALUES FROM (500) TO (600);