doc:  update release note item about the v2 wire protocol
Protocol v2 was last used in PG 7.3, not 7.2.
Reported-by: Tatsuo Ishii
Discussion:
@@ -213,7 +213,7 @@ Author: Heikki Linnakangas <heikki.linnakangas@iki.fi>
</para>
<para>
- This was last used as the default in Postgres 7.2 (year 2002).
+ This was last used as the default in Postgres 7.3 (year 2002).
</para>
</listitem>
