fix: move CSS from Blocks constructor to launch() for Gradio 6.0

Fixes UserWarning about deprecated css parameter in gr.Blocks().

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

app.py

@@ -338,7 +338,7 @@ def render_cloned_voices_html(voices_list):
 
 
 # Gradio Application Core setup
-with gr.Blocks(css=css_code, title="VoiceBook Gradio Hub") as demo:
+with gr.Blocks(title="VoiceBook Gradio Hub") as demo:
 
     books_state = gr.State(mock_books)
     voices_state = gr.State(mock_voices)
@@ -970,4 +970,4 @@ with gr.Blocks(css=css_code, title="VoiceBook Gradio Hub") as demo:
     )
 
 if __name__ == "__main__":
-    demo.queue().launch(allowed_paths=[str(Path(__file__).parent / "assets")])
+    demo.queue().launch(css=css_code, allowed_paths=[str(Path(__file__).parent / "assets")])