fix centrifugo demo link

README.md

@@ -297,7 +297,7 @@ _See also: [Comparison of CalDAV and CardDAV implementations - Wikipedia](https:
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 - [BluetoothCommunicatorExample](https://github.com/niedev/BluetoothCommunicatorExample) - Bluetooth LE chat app to communicate between android devices with P2P architecture. ([Clients](https://github.com/niedev/RTranslator)) `Apache-2.0` `Java`
-- [Centrifugo](https://centrifugal.dev/) - Language-agnostic real-time messaging (Websocket or SockJS) server. ([Demo]([https://github.com/centrifugal/centrifugo#demo](https://centrifugo3.herokuapp.com/)), [Source Code](https://github.com/centrifugal/centrifugo)) `MIT` `Go`
+- [Centrifugo](https://centrifugal.dev/) - Language-agnostic real-time messaging (Websocket or SockJS) server. ([Demo](https://github.com/centrifugal/centrifugo#demo), [Source Code](https://github.com/centrifugal/centrifugo)) `MIT` `Go`
 - [Chaskiq](https://chaskiq.io) - Full featured livechat, helpcenter and CRM as an alternative to Intercom & Drift, Crisp and others. ([Source Code](https://github.com/chaskiq/chaskiq)) `AGPL-3.0` `Ruby`
 - [Chatwoot](https://www.chatwoot.com) - Self-hosted customer communication platform, an alternative to Intercom & Zendesk. ([Source Code](https://github.com/chatwoot/chatwoot)) `MIT` `Ruby`
 - [Cherry](https://github.com/rafael-santiago/cherry) - Tiny webchat server. `GPL-2.0` `Go`