fix: remove broken plume demo link (error 502)

README.md

@@ -201,7 +201,7 @@ See also [Static Site Generators](#static-site-generators), [Content Management
 - [htmly](https://www.htmly.com/) - Databaseless Blogging Platform (Flat-File Blog). ([Demo](https://www.htmly.com/demo/), [Source Code](https://github.com/danpros/htmly)) `GPL-2.0` `PHP`
 - [Known](https://withknown.com/) - Single website for all your content. ([Source Code](https://github.com/idno/idno)) `Apache-2.0` `PHP`
 - [Noddity](http://noddity.com/) - It's a blog, it's a wiki, it's a fast CMS. ([Source Code](https://github.com/TehShrike/noddity)) `WTFPL` `Nodejs`
-- [Plume](https://joinplu.me/) - Federated blogging engine, based on ActivityPub. ([Demo](https://baptiste.gelez.xyz/), [Source Code](https://github.com/Plume-org/Plume)) `AGPL-3.0` `Ruby`
+- [Plume](https://joinplu.me/) - Federated blogging engine, based on ActivityPub. ([Source Code](https://github.com/Plume-org/Plume)) `AGPL-3.0` `Ruby`
 - [PluXml](http://www.pluxml.org/) - XML-based blog/CMS platform. ([Source Code](https://github.com/pluxml/PluXml)) `GPL-1.0` `PHP`
 - [Postleaf](https://www.postleaf.org/) - Open source blogging platform with inline editing, handlebar templates, and a beautiful user interface. ([Source Code](https://github.com/Postleaf/postleaf)) `MIT` `Nodejs`
 - [Solo](http://b3log.org/) - Blogging system written in Java, feel free to create your or your team own blog. ([Demo](http://88250.b3log.org/), [Source Code](https://github.com/b3log/solo)) `Apache-2.0` `Java`