docs/154934: typo fix #2 "is is" -> "is"

[eadler at FreeBSD.org]

Synopsis: typo fix #2 "is is" -> "is"

Responsible-Changed-From-To: freebsd-bugs->freebsd-doc
Responsible-Changed-By: eadler
Responsible-Changed-When: Tue Feb 22 22:29:27 EST 2011
Responsible-Changed-Why: 
assign to doc 

http://www.freebsd.org/cgi/query-pr.cgi?pr=154934