docs: Update Piper repo URL (#4231)

Author: salim-b

piper/README.md

@@ -2,7 +2,7 @@
 
 ![Supports aarch64 Architecture][aarch64-shield] ![Supports amd64 Architecture][amd64-shield]
 
-Home Assistant add-on that uses [piper](https://github.com/rhasspy/piper/) for text-to-speech.
+Home Assistant add-on that uses [piper](https://github.com/OHF-Voice/piper1-gpl) for text-to-speech.
 
 Part of the [Year of Voice](https://www.home-assistant.io/blog/2022/12/20/year-of-voice/).