fix namespace for community metric

Only "canonical" metrics (i.e. metrics implemented in `evaluate`) don't need a namespace. For the others you need to prepend the user.

app.py

@@ -2,5 +2,5 @@ import evaluate
 from evaluate.utils import launch_gradio_widget
 
 
-module = evaluate.load("directional_bias_amplification")
+module = evaluate.load("angelina-wang/directional_bias_amplification")
 launch_gradio_widget(module)