remove mailpile (development halted in May 2022)

- https://github.com/mailpile/Mailpile/commit/0989ac1fe341d969ab2cc4d35af5625b3a122964
- ref. https://github.com/awesome-selfhosted/awesome-selfhosted/issues/2266

README.md

@@ -452,7 +452,6 @@ Simple deployment of [E-mail](https://en.wikipedia.org/wiki/Email) servers, e.g.
 - [IMP](https://www.horde.org/apps/imp/) - HORDE application that provides webmail access to IMAP and POP3 accounts. ([Demo](http://demo.horde.org/), [Source Code](https://www.horde.org/download/imp)) `GPL-2.0` `PHP`
 - [Isotope Mail](https://blog.marcnuri.com/isotope-mail-client-introduction/) - Microservice based webmail client built with ReactJS and Spring. ([Source Code](https://github.com/manusa/isotope-mail)) `Apache-2.0` `Docker/Java`
 - [MailCare](https://mailcare.io) - Open source disposable email address service. ([Source Code](https://github.com/mailcare/mailcare)) `MIT` `PHP`
-- [Mailpile](https://www.mailpile.is/) - Webmail client with search, filtering, encryption features and more. ([Source Code](https://github.com/mailpile/Mailpile)) `AGPL-3.0` `Python`
 - [Roundcube](https://roundcube.net) - Browser-based IMAP client with an application-like user interface. ([Source Code](https://github.com/roundcube/roundcubemail)) `GPL-3.0` `PHP`
 - [SnappyMail](https://snappymail.eu/) - Simple, modern, lightweight & fast web-based email client. (It is an actively developed fork of RainLoop). ([Demo](https://snappymail.eu/demo/), [Source Code](https://github.com/the-djmaze/snappymail)) `AGPL-3.0` `PHP`
 - [SquirrelMail](https://squirrelmail.org) - Another browser-based IMAP client. ([Source Code](https://sourceforge.net/p/squirrelmail/code/HEAD/tree/)) `GPL-2.0` `PHP`