Remove inotify example code when MK_EXAMPLES == no

This change adds the needed entries to OLD_DIRS and OLD_FILES to ensure
that the paths are properly cleaned up when make delete-old is run and
MK_EXAMPLES == no.

MFC after: 2 months
Fixes: 1d8664d69041 ("examples: Add a demo program for inotify")
Differential Revision: https://reviews.freebsd.org/D51934