Update Authors and version on README

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

.github/CODEOWNERS

@@ -1,7 +0,0 @@
-# Each line is a file pattern followed by one or more owners.
-
-# These owners will be the default owners for everything in
-# the repo. Unless a later match takes precedence,
-# @global-owner1 and @global-owner2 will be requested for
-# review when someone opens a pull request.
-*       @EnterpriseDB/repmgr-dev

README.md

@@ -7,8 +7,8 @@ replication capabilities with utilities to set up standby servers, monitor
 replication, and perform administrative tasks such as failover or switchover
 operations.
 
-The most recent `repmgr` version (5.3.2) supports all PostgreSQL versions from
-9.5 to 15. PostgreSQL 9.4 is also supported, with some restrictions.
+The most recent `repmgr` version (5.4.1) supports all PostgreSQL versions from
+10 to 16.
 
 `repmgr` is distributed under the GNU GPL 3 and maintained by EnterpriseDB.
 
@@ -56,8 +56,6 @@ There is a mailing list/forum to discuss contributions or issues:
 
 * https://groups.google.com/group/repmgr
 
-The IRC channel #repmgr is registered with freenode.
-
 Please report bugs and other issues to:
 
 * https://github.com/EnterpriseDB/repmgr
@@ -69,6 +67,14 @@ news are always welcome.
 
 Thanks from the repmgr core team.
 
+* Ian Barwick
+* Israel Barth
+* Mario González
+* Martín Marqués
+* Gianni Ciolli
+
+Past contributors:
+
 * Jaime Casanova
 * Abhijit Menon-Sen
 * Simon Riggs