Reword the sentence for pg_logical_slot_peek_changes function.

Previously the duplicated paragraphs were used next to each other
in the document to demonstrate that the changes in the stream
were not consumed by pg_logical_slot_peek_changes function.
But some users misunderstood that the duplication of the same
paragraph was just typo. So this commit rewords the sentence in
the latter paragraph for less confusing.

Christoph Moench-Tegeder

doc/src/sgml/logicaldecoding.sgml

@@ -114,7 +114,7 @@ postgres=# SELECT * FROM pg_logical_slot_peek_changes('regression_slot', NULL, N
  0/16E0B90 | 690 | COMMIT 690
 (3 rows)
 
-postgres=# -- You can also peek ahead in the change stream without consuming changes
+postgres=# -- The next call to pg_logical_slot_peek_changes() returns the same changes again
 postgres=# SELECT * FROM pg_logical_slot_peek_changes('regression_slot', NULL, NULL);
  location  | xid |                     data
 -----------+-----+-----------------------------------------------