Update app.py

fix incorrect resolution steps issues that may block generation

app.py

@@ -255,14 +255,14 @@ with gr.Blocks(css=css, theme="xiaobaiyuan/theme_brief") as demo:
                 label="Width",
                 minimum=512,
                 maximum=2048,
-                step=8,
+                step=64,
                 value=1024,
             )
             height = gr.Slider(
                 label="Height",
                 minimum=512,
                 maximum=2048,
-                step=8,
+                step=64,
                 value=1024,
             )
         with gr.Row():