Remove claim that there's no Unix puttygen

[originally from svn r3860]

unix/putty.1

@@ -148,6 +148,3 @@ the manual on the web page:
 \fBhttp://www.chiark.greenend.org.uk/~sgtatham/putty/\fP
 .SH BUGS
 This man page isn't terribly complete.
-
-It's not very helpful to require a PuTTY-format SSH2 key file when
-there isn't yet a Unix port of PuTTYgen.