mail/mu4e-maildirs: Mark as BROKEN and deprecate

The port does not build with recent versions of mail/mu due to missing
a required file. So mark it as BROKEN.

The upstream added two years ago a deprecation notice which
discourages use of this software and recommends to switch to use
mail/mu, which now integrates the features provided by this
software. So deprecate the port and set to expire on 2025-11-30.

While here, switch dependency on mail/mu4e to mail/mu for unbreaking
make index.

PR: 289593
Reported by: yasu (via ports-committers)
Approved by: hrs (maintainer, implicit)