fix the u2 export, test=asr

paddlespeech/s2t/exps/u2/model.py

@@ -524,10 +524,10 @@ class U2Tester(U2Trainer):
             List[paddle.static.InputSpec]: input spec.
         """
         from paddlespeech.s2t.models.u2 import U2InferModel
-        infer_model = U2InferModel.from_pretrained(self.train_loader,
+        infer_model = U2InferModel.from_pretrained(self.test_loader,
                                                    self.config.clone(),
                                                    self.args.checkpoint_path)
-        feat_dim = self.train_loader.feat_dim
+        feat_dim = self.test_loader.feat_dim
         input_spec = [
             paddle.static.InputSpec(shape=[1, None, feat_dim],
                                     dtype='float32'),  # audio, [B,T,D]