mail/courier-imap: Fix inotify support on FreeBSD 15 and up

FreeBSD 15 introduced a native inotify implementation in libc; avoid
depending and linking libinotify on these relases, since it interferes
with the libc implementation.

MFH: 2026Q1
(cherry picked from commit c6a80d646d95392f13da873351a68c79d1c2efec)