Only check ssh protocol if openssh < 7.0

OpenSSH made the `Protocol` option obsolete in version 7.0. Even if you
try to specify it, it's not going to use the version you set for
security reasons:

  Potentially-incompatible Changes
  --------------------------------

   * Support for the legacy SSH version 1 protocol is disabled by
     default at compile time.

See the release notes for version 7.0 for more details.

https://www.openssh.org/releasenotes.html

Author: rhmdnd

linux_os/guide/services/ssh/ssh_server/sshd_allow_only_protocol2/rule.yml

@@ -65,3 +65,4 @@ template:
         parameter: Protocol
         value: "2"
         datatype: int
+        obsolete_since_version: "7.0"