[9.x] Added new env options for v3 sftp adaptor

[dunhamjared]

Added new possible values for the SFTP Driver Configuration example.

The new optional values were added to match the order of the arguments for: League\Flysystem\PhpseclibV3\SftpConnectionProvider.

return new SftpConnectionProvider(
    $options['host'],
    $options['username'],
    $options['password'] ?? null,
    $options['privateKey'] ?? null,
    $options['passphrase'] ?? null,
    $options['port'] ?? 22,
    $options['useAgent'] ?? false,
    $options['timeout'] ?? 10,
    $options['maxTries'] ?? 4,
    $options['hostFingerprint'] ?? null,
    $options['connectivityChecker'] ?? null
);