manual.texi fixed typo

with some effort a clever attacker can crack the password if he is able

to sniff the traffic between the client and the server. If the 

connection between the client and the server goes through an untrusted

network, you should use an @strong(SSH} tunnel to encrypt the 

network, you should use an @strong{SSH} tunnel to encrypt the 

communication.

All other information is transferred as text that can be read by anyone