dns/dnsmasq-devel: remove port, dns/dnsmasq is newer

Due to administrative issues effectuated earlier in 2026 that have been
unresolved to date, this port been unable to move usefully fast enough.

Let's not pretend otherwise and remove the dnsmasq-devel port,
as announced in its DEPRECATED tag, now that dns/dnsmasq is newer
than this dns/dnsmasq-devel; the DEPRECATED has announced for months
this would happen after dnsmasq's v2.93 release. (There was no
EXPIRATION_DATE because the v2.93 release wasn't fixed to a date.)

Add MOVED and UPDATING entries to suggest that
users should install the stable dns/dnsmasq port instead.

In order to minimize disruption on the quarterly branch, this shall not
be MFH'd, I will propose to update dnsmasq-devel to 2.93 release for
2026Q2 by direct commit instead.

PR: 295851
Pull Request: https://github.com/freebsd/freebsd-ports/pull/529