Minor cleanup related to pg_wal_replay_wait() procedure
* Rename $node_standby1 to $node_standby in 043_wal_replay_wait.pl as there
is only one standby.
* Remove useless debug printing in 043_wal_replay_wait.pl.
* Fix typo in one check description in 043_wal_replay_wait.pl.
* Fix some wording in comments and documentation.
Reported-by: Alexander Lakhin
Discussion: https://postgr.es/m/
1d7b08f2-64a2-77fb-c666-
c9a74c68eeda%40gmail.com
Reviewed-by: Alexander Lakhin