Update about.md

Remove Friedrich from team listing in about.md

content/about.md

@@ -17,11 +17,10 @@ eMail: info[at]monal[minus]im[dot]org
 
 Monal originates in 2002 as fork of the SworIM app.
 Until 2019 it has been developed by Anu Pokharel.
-Since then Thilo Molitor took over the development and joined in 2020 with Friedrich Altheide.
+Since then Thilo Molitor took over the development and joined in 2020 with Friedrich Altheide (until 2024).
 From initial rewrite of code in the backend the entire app has been upgraded with a modern XMPP engine, new features and future-proof setup.
 Monal challenges to be the go-to XMPP chat-app for the iOS and macOS platform.
 
 ## Monal Team
 
 **Thilo Molitor** - [About me on wiki.xmpp.org](https://wiki.xmpp.org/web/User:TMolitor)  
-**Friedrich Altheide**