textproc/m17n-im-config: Deprecate and set expiration date to 2025-03-31

WWW is non resolvable (NXDOMAIN), looking at other m17n related ports,
it seems that current site is https://www.nongnu.org/m17n/

However I can't find distfile at project site or SAVANNAH/m17n mirrors.

PR: 284818
Approved by: maintainer timeout >2 weeks, portmgr (blanket)