Upgraded PMD version to 6.21.0
Upgraded PMD version to 6.21.0

lgoldstein/mina-sshd,lgoldstein/mina-sshd,apache/mina-sshd,apache/mina-sshd,apache/mina-sshd,apache/mina-sshd,lgoldstein/mina-sshd,lgoldstein/mina-sshd