Fix release date

Author: dmpgpro

doc/src/sgml/release-pro-9.6.sgml

@@ -4,7 +4,7 @@
   <title>Postgres Pro 9.6.3.1</title>
   <note>
     <title>Release Date</title>
-    <simpara>2017-05-12</simpara>
+    <simpara>2017-05-15</simpara>
   </note>
   <sect2>
     <title>Overview</title>