refactor: update generate image button label

app.py

@@ -196,7 +196,7 @@ with gr.Blocks() as demo:
         with gr.Row():
             prompt = gr.Textbox(label='Enter your prompt (English)', scale=8)
             submit_prompt = gr.Button(
-                scale=1, variant='primary', label='Generate Image')
+                'Generate Image', scale=1, variant='primary')
             img = gr.Image(label='SDXL-Lightning Generated Image')
 
     with gr.Row(variant="panel"):