add unilm base uncased config

unilm-base-uncased-config.json

@@ -12,7 +12,5 @@
     "num_hidden_layers": 12,
 	"pad_token_id": 0,
     "type_vocab_size": 2,
-	"is_encoder_decoder": 1,
-	"is_prefix_model": 1,
     "vocab_size": 30522
 }