removed model_type key to fix initialization error

config.json

@@ -1 +1 @@
-{"model_type": "gptsan-japanese", "d_model": 768, "n_layer": 24, "vocab_size": 32000, "ssm_cfg": {}, "rms_norm": true, "residual_in_fp32": true, "fused_add_norm": true, "pad_vocab_size_multiple": 8}
+{"d_model": 768, "n_layer": 24, "vocab_size": 32000, "ssm_cfg": {}, "rms_norm": true, "residual_in_fp32": true, "fused_add_norm": true, "pad_vocab_size_multiple": 8}