clean up notebook format

remove top level header so the doc website will render correctly.

Author: junpenglao

docs/source/notebooks/blackbox_external_likelihood.ipynb

@@ -1032,17 +1032,17 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "# Authors\n",
+    "## Authors\n",
     "\n",
     "* Adapted from a blog post by [Matt Pitkin](http://mattpitkin.github.io/samplers-demo/pages/pymc3-blackbox-likelihood/) on August 27, 2018. That post was based on an example provided by [Jørgen Midtbø](https://github.com/jorgenem/)."
    ]
   }
  ],
  "metadata": {
   "kernelspec": {
-   "display_name": "Python 3.6 (testing)",
+   "display_name": "Python 3",
    "language": "python",
-   "name": "testing"
+   "name": "python3"
   },
   "language_info": {
    "codemirror_mode": {
@@ -1054,7 +1054,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.6.6"
+   "version": "3.6.5"
   }
  },
  "nbformat": 4,