Bump Log4j2 version to 2.16.0

The Apache Log4j team have just released version 2.16.0 which is a drop-in replacement for previous 2.x versions like the 2.15.0 version now being downloaded by the launcher.

 

2.16.0 hardens Log4j against the CVE which 2.15.0 fixes and it would be a nice version bump to disable the vulnerable feature entirely.

 

See changes here: https://logging.apache.org/log4j/2.x/changes-report.html#a2.16.0