Summary:
Bump to version 8.0.4 from 2024-09-11 per https://github.com/php-mime-mail-parser/php-mime-mail-parser/releases before this ancient code copy falls apart.
`scripts/mail/mail_handler.php` (used for incoming (!) mail) is the only consumer.
Closes T15940
Test Plan: Feed `mail_handler.php` with various test emails (formats: plain text, HTML, multipart; encodings: UTF-8, ASCII, ISO-8859-something) by manually replacing `php://stdin` with corresponding text files and adding some `phlog`s for output checking as I don't have mail server glue handy. Get only expected errors for broken emails.
Reviewers: O1 Blessed Committers, 20after4
Reviewed By: O1 Blessed Committers, 20after4
Subscribers: 20after4, tobiaswiese, valerio.bozzolan, Matthew, Cigaryno
Maniphest Tasks: T15940
Differential Revision: https://we.phorge.it/D25829
