Ultralytics Asset URL Update (#13181)

Refactor code for speed and clarity

tutorial.ipynb

@@ -170,7 +170,7 @@
       },
       "source": [
         "# Download COCO val\n",
-        "torch.hub.download_url_to_file('https://ultralytics.com/assets/coco2017val.zip', 'tmp.zip')  # download (780M - 5000 images)\n",
+        "torch.hub.download_url_to_file('https://github.com/ultralytics/assets/releases/download/v0.0.0/coco2017val.zip', 'tmp.zip')  # download (780M - 5000 images)\n",
         "!unzip -q tmp.zip -d ../datasets && rm tmp.zip  # unzip"
       ],
       "execution_count": null,
@@ -326,7 +326,7 @@
             "\u001b[34m\u001b[1mTensorBoard: \u001b[0mStart with 'tensorboard --logdir runs/train', view at http://localhost:6006/\n",
             "\n",
             "Dataset not found ⚠️, missing paths ['/content/datasets/coco128/images/train2017']\n",
-            "Downloading https://ultralytics.com/assets/coco128.zip to coco128.zip...\n",
+            "Downloading https://github.com/ultralytics/assets/releases/download/v0.0.0/coco128.zip to coco128.zip...\n",
             "100% 6.66M/6.66M [00:00<00:00, 75.6MB/s]\n",
             "Dataset download success ✅ (0.6s), saved to \u001b[1m/content/datasets\u001b[0m\n",
             "\n",