Update requirements.txt

When you clone this repository and run the `app.py` file, install the `gradio` library to fix this error message:
```bash Public/voice-chat-with-mistral/app.py", line 19, in <module>
import gradio as gr
ModuleNotFoundError: No module named 'gradio'```

requirements.txt

@@ -8,10 +8,12 @@ mecab-python3==1.0.6
 unidic-lite==1.0.8
 unidic==1.1.0
 langid
+gradio
 deepspeed
 pydub
 librosa
 ffmpeg-python
+gradio
 gradio_client
 emoji
 asyncio