fix link on contribute/docs page

It was broken in d18c835#diff-89f8d80a3fb313d1d00abbc99eb5c180

Author: Molkree

site/en/community/contribute/docs.md

@@ -257,7 +257,7 @@ is a hosted notebook environment that makes it easy to edit—and run—notebook
 documentation. Notebooks in GitHub are loaded in Google Colab by passing the
 path to the Colab URL, for example,
 the notebook located in GitHub here:
-<a href="https://   &#103;ithub.com/tensorflow/docs/blob/master/site/en/tutorials/keras/classification.ipynb">https://  &#103;ithub.com/tensorflow/docs/blob/master/site/en/tutorials/keras/classification.ipynb</a><br/>
+<a href="https://github.com/tensorflow/docs/blob/master/site/en/tutorials/keras/classification.ipynb">https://github.com/tensorflow/docs/blob/master/site/en/tutorials/keras/classification.ipynb</a><br/>
 can be loaded into Google Colab at this URL:
 <a href="https://colab.research.google.com/github/tensorflow/docs/blob/master/site/en/tutorials/keras/classification.ipynb">https://colab.research.google.com/github/tensorflow/docs/blob/master/site/en/tutorials/keras/classification.ipynb</a>