Bug#804077: parallel-ssh manpage: typo: paralllel -> parallel

[Peter Gervai]

Package: pssh
Version: 2.3.1-1
Followup-For: Bug #804077

Regardless of the years going by this report is still valid. 

Mind you, I realize that the package wasn't touched since 2014
and that its upstream changed and moved. NMU time? :-)