doc: properly attibute PG 12 pgbench release note item

Reported-by: Fabien COELHO

Discussion: https://postgr.es/m/alpine.DEB.2.21.1905130839140.13487@lancre

doc/src/sgml/release-12.sgml

@@ -2283,7 +2283,7 @@ Author: Peter Eisentraut <peter_e@gmx.net>
 2018-10-15 [5b75a4f82] pgbench: Report errors during run better
 -->
 <para>
-Improve pgbench error reporting with clearer messages and return codes (Fabien Coelho)
+Improve pgbench error reporting with clearer messages and return codes (Peter Eisentraut)
 </para>
 </listitem>