Update chunk_decode.yaml

examples/aishell/asr0/conf/tuning/chunk_decode.yaml

-chunk_batch_size: 32
+decode_batch_size: 32
 error_rate_type: cer 
 decoding_method: ctc_beam_search
 lang_model_path: data/lm/zh_giga.no_cna_cmn.prune01244.klm
 alpha: 2.2 #1.9
 beta: 4.3
-beam_size: 300
+beam_size: 500
 cutoff_prob: 0.99
 cutoff_top_n: 40
 num_proc_bsearch: 10