Update `umami` demo + repo link (#3636)

This is the current demo URL from umami.is, and it is a better demo as it gets a lot more traffic than flightphp.com.

README.md

@@ -137,7 +137,7 @@ _Related: [Personal Dashboards](#personal-dashboards)_
 - [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`
 - [Superset](http://superset.apache.org/) - Mmodern data exploration and visualization platform. ([Source Code](https://github.com/apache/superset)) `Apache-2.0` `Python`
-- [Umami](https://umami.is/) - Simple, fast, privacy-focused alternative to Google Analytics. ([Demo](https://app.umami.is/share/ISgW2qz8/flightphp.com), [Source Code](https://github.com/mikecao/umami)) `MIT` `Nodejs`
+- [Umami](https://umami.is/) - Simple, fast, privacy-focused alternative to Google Analytics. ([Demo](https://app.umami.is/share/8rmHaheU/umami.is), [Source Code](https://github.com/umami-software/umami)) `MIT` `Nodejs`
 
 
 ### Archiving and Digital Preservation (DP)