Project URL pointing to non-existing GitHub Pages site

[de-code]

The Project URL in setup.py is pointing to https://allenai.github.io/SciSpaCy/ which doesn't exist.
In the absence of that, it should point to https://github.com/allenai/scispacy.

(The Project URL is for example displayed on PyPI)

[dakinggg]

Thanks! Feel free to open a PR fixing this if you like.