Align configuration with BiRefNet ONNX template

config.json

@@ -1,3 +1,3 @@
 {
   "model_type": "birefnet"
-}
+}

preprocessor_config.json

@@ -20,4 +20,4 @@
     "height": 1024,
     "width": 1024
   }
-}
+}