sshserver: fix excluding obsolete client config lines

sshserver: fix excluding obsolete client config lines

It was already excluded for OpenSSH-Windows. Extend it to all OpenSSH
above v7.3. Syncing up this logic with the sshd server config.

Fixing, in `sftp_server.log`:
```
log/server/curl_sftp_config line 33: Unsupported option "rhostsrsaauthentication"
log/server/curl_sftp_config line 34: Unsupported option "rsaauthentication"
```

`no` has been the default for these since OpenSSH 3.3 (2002-06-21).

Closes #16784