remove broken Redash demo link (#3788)

- ref.https://github.com/awesome-selfhosted/awesome-selfhosted/issues/3558
- https://demo.redash.io/ : HTTPSConnectionPool(host='demo.redash.io', port=443): Max retries exceeded with url: / (Caused by NewConnectionError('<urllib3.connection.HTTPSConnection object at 0x7ff3dc2643a0>: Failed to establish a new connection: [Errno -2] Name or service not known'))

README.md

@@ -133,7 +133,7 @@ _Related: [Personal Dashboards](#personal-dashboards)_
 - [Open Web Analytics](http://www.openwebanalytics.com/) - Web analytics framework that lets you stay in control of how you instrument and analyze the use of your websites and applications. ([Source Code](https://github.com/padams/Open-Web-Analytics)) `GPL-2.0` `PHP`
 - [Plausible Analytics](https://plausible.io/) - Simple, open-source, lightweight (< 1 KB) and privacy-friendly web analytics. ([Source Code](https://github.com/plausible/analytics/)) `MIT` `Elixir`
 - [PostHog](https://posthog.com) - Product analytics, session recording, feature flagging and a/b testing that you can self-host. Alternative to Mixpanel/Amplitude/Heap/HotJar/Optimizely. ([Source Code](https://github.com/posthog/posthog)) `MIT` `Python`
-- [Redash](http://redash.io) - Connect and query your data sources, build dashboards to visualize data and share them with your company. ([Demo](https://demo.redash.io), [Source Code](https://github.com/getredash/redash)) `BSD-2-Clause` `Docker`
+- [Redash](http://redash.io) - Connect and query your data sources, build dashboards to visualize data and share them with your company. ([Source Code](https://github.com/getredash/redash)) `BSD-2-Clause` `Docker`
 - [RudderStack](https://rudderstack.com/) - Collect, unify, transform, and store your customer data, and route it to a wide range of common, popular marketing, sales, and product tools. alternative to Segment. ([Source Code](https://github.com/rudderlabs/rudder-server/)) `AGPL-3.0` `Docker/K8S/Go/Nodejs`
 - [Shynet](https://github.com/milesmcc/shynet) - Modern, privacy-friendly, and detailed web analytics that works without cookies or JS. `Apache-2.0` `Python`
 - [Socioboard](https://github.com/socioboard/Socioboard-4.0) `⚠` - Social media management, analytics, and reporting platform supporting nine social media networks out-of-the-box. `GPL-3.0` `Nodejs`