Remove unused repos

[Conengmo]

• can we remove the https://github.com/python-visualization/folium_contrib repo? I don't think it's relevant anymore...
• I'm pretty sure we can also remove https://github.com/python-visualization/Leaflet.awesome-markers. We created that fork since somebody offered to make improvements on it. But that never happened, and we never started using this fork. See Font Awesome fonts built under version 5 don't render in folium 0.5.0 #923 (comment).

[ocefpaf]

Yep. Go for it!

[Conengmo]

Done! Thanks!