Update README.md

darcs.net is down, removing it from the links.

README.md

@@ -42,7 +42,6 @@ Thanks to the [Decentralized Web Summit](https://www.decentralizedweb.net/) for
 * [git-ssb](https://github.com/clehner/git-ssb) - Decentralized git repo hosting and issue tracking on secure-scuttlebutt.
 * [PeerPad](https://peerpad.net) - a realtime P2P collaborative editing tool, powered by IPFS and CRDTs.
 * [Radicle](https://radicle.xyz/) - secure peer-to-peer code collaboration without intermediaries.
-* [darcs](http://darcs.net/) - Darcs(Darcs Advanced Revision Control System) is a distributed version control system.
 * [Pijul](https://pijul.org/) - Pijul is a free and open source (GPL2) distributed version control system.
 
 ### Communication