Changed the value of label_width to 600 to handle full coco dataset

Author: xzhou33

introduction_to_amazon_algorithms/object_detection_pascalvoc_coco/object_detection_image_json_format.ipynb

@@ -427,7 +427,7 @@
     "                             overlap_threshold=0.5,\n",
     "                             nms_threshold=0.45,\n",
     "                             image_shape=512,\n",
-    "                             label_width=350,\n",
+    "                             label_width=600,\n",
     "                             num_training_samples=4452)"
    ]
   },