fix mobility notebook link

README.md

@@ -176,7 +176,7 @@ useful helper and plotting functions that are used in the sample notebooks.
 </td>
 <td><a href="https://renkulab.io/datasets/46c02f05-393a-4a78-bd5d-d3bf2c23d577">Measures of social distancing</a></td>
 <td><code>data/distancing-metrics</code></td>
-<td>https://renkulab.io/projects/covid-19/covid-19-public-data/files/blob/notebooks/examples/distancing-measures.ipynb</td>
+<td><a href="https://renkulab.io/projects/covid-19/covid-19-public-data/files/blob/notebooks/examples/distancing-measures.ipynb">notebooks/examples/distancing-measures.ipynb</a></td>
 </tr>
 </tbody>
 </table>