Correct path for blacklistd.conf in OptionalObsoleteFiles.inc

Fix typo made when adding the blacklistd.conf file to OptionalObsoleteFiles.inc

Submitted by: Herbert J. Skuhra ( herbert at mailbox.org )
Reviewed by: rpaulo
Approved by: rpaulo
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D6715