Update demo link for Wallabag

The link to http://demo.wallabag.org/ is no longer working, currently pointing to an nginx welcome page. New link should be https://app.wallabag.it/register/

README.md

@@ -1216,7 +1216,7 @@ See also _[Monitoring](#monitoring)_
 **[`^        back to top        ^`](#)**
 
 - [Nunux Keeper](http://keeper.nunux.org/) - Your personal content curation service. ([Source Code](https://github.com/ncarlier/nunux-keeper)) `GPL-3.0` `Nodejs`
-- [Wallabag](https://www.wallabag.org) - Wallabag, formerly Poche, is a web application allowing you to save articles to read them later with improved readability. ([Demo](http://demo.wallabag.org/), [Source Code](https://github.com/wallabag/wallabag)) `MIT` `PHP`
+- [Wallabag](https://www.wallabag.org) - Wallabag, formerly Poche, is a web application allowing you to save articles to read them later with improved readability. ([Demo](https://app.wallabag.it/register/), [Source Code](https://github.com/wallabag/wallabag)) `MIT` `PHP`
 
 ## Resource Planning