Doc: fix bogus to_date() examples.

November doesn't have 31 days.  Remarkably, this thinko
has escaped detection since commit 3f1998727.

Noted by Y. Saburov.

Discussion: https://postgr.es/m/171276122213.681.531905738590773705@wrigleys.postgresql.org

doc/src/sgml/func.sgml

@@ -8285,11 +8285,11 @@ SELECT regexp_match('abc01234xyz', '(?:(.*?)(\d+)(.*)){1,1}');
        use some non-digit character or template after <literal>YYYY</literal>,
        otherwise the year is always interpreted as 4 digits. For example
        (with the year 20000):
-       <literal>to_date('200001131', 'YYYYMMDD')</literal> will be
+       <literal>to_date('200001130', 'YYYYMMDD')</literal> will be
        interpreted as a 4-digit year; instead use a non-digit
        separator after the year, like
-       <literal>to_date('20000-1131', 'YYYY-MMDD')</literal> or
-       <literal>to_date('20000Nov31', 'YYYYMonDD')</literal>.
+       <literal>to_date('20000-1130', 'YYYY-MMDD')</literal> or
+       <literal>to_date('20000Nov30', 'YYYYMonDD')</literal>.
       </para>
      </listitem>