fix: correct remaining -c to -C in man page example

Fixed last instance of old cluster option in ping command example

Author: inureyes

docs/man/bssh.1

@@ -307,7 +307,7 @@ Use cluster from configuration:
 
 .TP
 Test connectivity:
-.B bssh -c production ping
+.B bssh -C production ping
 
 .TP
 Upload file to remote hosts (SFTP):