remove dyu comments (unmaintained since 2019) (#3709)

- develpment requires EOL Java 7
- no activity in issues since 2017
- ref. #3558

README.md

@@ -536,7 +536,6 @@ Simple deployment of [E-mail](https://en.wikipedia.org/wiki/Email) servers, e.g.
 - [Coral](https://coralproject.net/) - A better commenting experience from Vox Media. ([Source Code](https://github.com/coralproject/talk)) `Apache-2.0` `Nodejs`
 - [diaspora*](https://diasporafoundation.org/) - Distributed social networking server. ([Source Code](https://github.com/diaspora/diaspora)) `AGPL-3.0` `Ruby`
 - [Discourse](https://www.discourse.org/) - Advanced forum / community solution based on Ruby and JS. ([Demo](https://try.discourse.org/), [Source Code](https://github.com/discourse/discourse)) `GPL-2.0` `Ruby`
-- [dyu comments](https://github.com/dyu/comments) - Real-time, markdown-enabled comment engine powered by leveldb. ([Demo](https://dyu.github.io/comments/real-time/)) `Apache-2.0` `Java`
 - [Elgg](https://elgg.org/) - Powerful open source social networking engine. ([Source Code](https://github.com/Elgg/Elgg)) `GPL-2.0` `PHP`
 - [Enigma 1/2 BBS](https://nuskooler.github.io/enigma-bbs/) - Enigma 1/2 is a modern, multi-platform BBS engine with unlimited "callers" and legacy DOS door game support. ([Demo](https://l33t.codes/xibalba-bbs/), [Source Code](https://github.com/NuSkooler/enigma-bbs)) `BSD-2-Clause` `Shell/Docker/Nodejs`
 - [EpochTalk](https://github.com/epochtalk/epochtalk) - Next Generation Forum Software. `MIT` `Nodejs`