Fix downloading COCO weights in demo.ipynb

samples/demo.ipynb

@@ -37,7 +37,7 @@
     "\n",
     "# Import Mask RCNN\n",
     "sys.path.append(ROOT_DIR)  # To find local version of the library\n",
-    "import mrcnn.utils\n",
+    "from mrcnn import utils\n",
     "import mrcnn.model as modellib\n",
     "from mrcnn import visualize\n",
     "# Import COCO config\n",