Update sshguard.rb

Apparently the url for the last applied patch has changed, probably due to some convention change at sourceforge itself.

New url is: http://sourceforge.net/p/sshguard/bugs/_discuss/thread/3d94b7ef/c062/attachment/sshguard.c.diff

sha1 hash for this file remains the same

Closes #32957.

Signed-off-by: Tim D. Smith <git@tim-smith.us>