upstream: correct keyword; from Yatao Su via GHPR509

OpenBSD-Commit-ID: 81c778c76dea7ef407603caa157eb0c381c52ad2

Author: djmdjm

sshd_config.5

@@ -1586,7 +1586,7 @@ accumulated.
 .Pp
 Penalties are enabled by default with the default settings listed below
 but may disabled using the
-.Cm off
+.Cm no
 keyword.
 The defaults may be overridden by specifying one or more of the keywords below,
 separated by whitespace.