Replace "checkpoint segment" with "WAL segment".
Reported-by: Maksim Milyutin <milyutinma@gmail.com>
<listitem>
<para>
Write a message to the server log if checkpoints caused by
- the filling of checkpoint segment files happen closer together
+ the filling of WAL segment files happen closer together
than this many seconds (which suggests that
<varname>max_wal_size</varname> ought to be raised). The default is
30 seconds (<literal>30s</literal>). Zero disables the warning.