Add 8.5.5 CHANGELOG items

[ci skip]

CHANGELOG.md

@@ -9,7 +9,11 @@ omnibus-gitlab repository.
 - Pass listen_network of gitlab_workhorse to gitlab nginx template 51b20e2
 - Enable NGINX proxy caching 8b91c071
 - Restart unicorn when bundled ruby is updated aca3cb2
-- Add ablity to use dateformat for logrotate configuration (Steve Norman)
+- Add ability to use dateformat for logrotate configuration (Steve Norman)
+
+8.5.5
+
+- Add ldap_sync_time global configuration as the EE is still supporting it
 8.5.4