fix env bug

docs/vibevoice-realtime-0.5b.md

@@ -99,7 +99,7 @@ sudo docker run --privileged --net=host --ipc=host --ulimit memlock=-1:-1 --ulim
 git clone https://github.com/microsoft/VibeVoice.git
 cd VibeVoice/
 
-pip install -e .
+pip install -e .[tts]
 ```
 
 ## Usages