Adding Postgres version 16 support in 5.4.1

We've done extensive testing of the current version of repmgr against the
new version 16 of Postgres. The tests have passed which gives us the
green light to add the version as supported in repmgr 5.4.1.

The commit only addresses documentation amendments

Signed-off-by: Martín Marqués <martin.marques@enterprisedb.com>

doc/appendix-release-notes.xml

@@ -18,9 +18,9 @@
   <!-- remember to update the release date in ../repmgr_version.h.in -->
   <sect1 id="release-5.4.1">
     <title id="release-current">Release 5.4.1</title>
-    <para><emphasis>??? ?? ??????, 202?</emphasis></para>
+    <para><emphasis>Tue 04 July, 2023</emphasis></para>
     <para>
-      &repmgr; 5.4.1 is a minor release providing ...
+      &repmgr; 5.4.1 is a minor release providing a fix for witness metadata update
     </para>
     <sect2>
       <title>Bug fixes</title>

doc/install-requirements.xml

@@ -120,13 +120,13 @@
               &repmgr; 5.4
             </entry>
             <entry>
-              (dev)
+              YES
             </entry>
             <entry>
               <link linkend="release-current">&repmgrversion;</link> (&releasedate;)
             </entry>
             <entry>
-              9.4, 9.5, 9.6, 10, 11, 12, 13, 15
+              10, 11, 12, 13, 14, 15, 16
             </entry>
             <entry>
               &nbsp;

doc/repmgr.xml

@@ -26,7 +26,7 @@
   <abstract>
    <para>
    This is the official documentation of &repmgr; &repmgrversion; for
-   use with PostgreSQL 9.4 - PostgreSQL 15.
+   use with PostgreSQL 9.4 - PostgreSQL 16.
    </para>
    <para>
      &repmgr; is being continually developed and we strongly recommend using the