change bart-large-cnn to bart-large in demo folder

demo/CustomBARTv4b_model-generate.ipynb

@@ -141,7 +141,7 @@
         "OUTPUT_VOCAB_SIZE = 16384 + 1  # encoded image token space + 1 for bos\n",
         "OUTPUT_LENGTH = 256 + 1  # number of encoded tokens + 1 for bos\n",
         "BOS_TOKEN_ID = 16384\n",
-        "BASE_MODEL = 'facebook/bart-large-cnn'"
+        "BASE_MODEL = 'facebook/bart-large'"
       ],
       "execution_count": 3,
       "outputs": []
@@ -563,4 +563,4 @@
       ]
     }
   ]
-}
+}