Update config.json

Add ` "processor_class": "Wav2Vec2Processor",`, so we can use `AutoProcessor` to load the processor.

config.json

@@ -234,6 +234,7 @@
   "forced_eos_token_id": 2,
   "is_encoder_decoder": true,
   "model_type": "speech-encoder-decoder",
+  "processor_class": "Wav2Vec2Processor",
   "pad_token_id": 1,
   "tie_word_embeddings": false,
   "tokenizer_class": "mbart50",