Fix sample output of EXPLAIN ANALYZE.

Since commit f0f13a3a08, we estimate
ModifyTable paths without a RETURNING clause differently.  Update an
example from the manual that showed the old behavior.

Author: Takayuki Tsunakawa <tsunakawa.takay@fujitsu.com>
Reviewed-by: Laurenz Albe <laurenz.albe@cybertec.at>
Discussion: https://postgr.es/m/TYAPR01MB29905674F41693BBA9DA28CAFEA20%40TYAPR01MB2990.jpnprd01.prod.outlook.com

doc/src/sgml/perform.sgml

@@ -773,7 +773,7 @@ EXPLAIN ANALYZE UPDATE tenk1 SET hundred = hundred + 1 WHERE unique1 < 100;
 
                                                            QUERY PLAN
 -------------------------------------------------------------------&zwsp;-------------------------------------------------------------
- Update on tenk1  (cost=5.07..229.46 rows=101 width=250) (actual time=14.628..14.628 rows=0 loops=1)
+ Update on tenk1  (cost=5.07..229.46 rows=0 width=0) (actual time=14.628..14.628 rows=0 loops=1)
    ->  Bitmap Heap Scan on tenk1  (cost=5.07..229.46 rows=101 width=250) (actual time=0.101..0.439 rows=100 loops=1)
          Recheck Cond: (unique1 < 100)
          ->  Bitmap Index Scan on tenk1_unique1  (cost=0.00..5.04 rows=101 width=0) (actual time=0.043..0.043 rows=100 loops=1)
@@ -809,7 +809,7 @@ ROLLBACK;
 EXPLAIN UPDATE parent SET f2 = f2 + 1 WHERE f1 = 101;
                                     QUERY PLAN
 -------------------------------------------------------------------&zwsp;----------------
- Update on parent  (cost=0.00..24.53 rows=4 width=14)
+ Update on parent  (cost=0.00..24.53 rows=0 width=0)
    Update on parent
    Update on child1
    Update on child2