remove scrollback

Scrollback is no longer maintained as per #1197

README.md

@@ -246,7 +246,6 @@ Some [Groupware](#groupware) solutions also feature calendar/address book editin
   * [RetroShare](http://retroshare.org) - Secured and decentralized communication system. Offers decentralized chat, forums, messaging, file transfer. ([Source Code](https://github.com/RetroShare/RetroShare)) `GPLv2` `С++`
   * [Ring](https://ring.cx/) - Free software for universal communication which respects freedoms and privacy of its users. ([Source Code](https://github.com/savoirfairelinux/ring-project)) `GPLv3` `C++`
   * [Rocket.Chat](https://rocket.chat/) - Teamchat solution similar to Gitter.im or Slack. ([Source Code](https://github.com/RocketChat/Rocket.Chat)) `MIT` `Nodejs`
-  * [Scrollback](https://scrollback.io/) - Embeddable cross-platform chat for communities. ([Source Code](https://github.com/scrollback/scrollback)) `AGPLv3` `Nodejs`
   * [Spectrum 2](http://spectrum.im/) - Spectrum 2 is an open source instant messaging transport.  It allows users to chat together even when they are using different IM networks. ([Source Code](https://github.com/hanzz/spectrum2)) `GPLv3` `C++`
   * [Spreed](https://www.spreed.me/) - WebRTC audio/video calls, conferencing server, and web client. ([Source Code](https://github.com/strukturag/spreed-webrtc)) `AGPLv3` `Go`
   * [Synapse](http://matrix.org/docs/projects/server/synapse.html) - A server for [Matrix](https://matrix.org/), an open standard for decentralized persistent communication. ([Source Code](https://github.com/matrix-org/synapse)) `Apache` `Python`