chore(sshd): exclude deprecated SSHv2 key exchange algorithms

Author: Piotr Domagała

rootfs/etc/ssh/sshd_config

@@ -26,3 +26,6 @@ TCPKeepAlive yes
 #AcceptEnv LANG LC_*
 Subsystem sftp /usr/lib/openssh/sftp-server
 UseDNS no
+Ciphers aes128-cbc,aes192-cbc,aes256-cbc,rijndael-cbc@lysator.liu.se,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com,chacha20-poly1305@openssh.com
+Kexalgorithms diffie-hellman-group-exchange-sha256,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,curve25519-sha256@libssh.org,gss-gex-sha1-,gss-group1-sha1-,gss-group14-sha1-
+MACs hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-512,hmac-sha2-256,umac-128@openssh.com