Stop pushing "latest" to CDN

[nicolaskruchten]

Since we've decided not to continue updating https://cdn.plot.ly/plotly-latest.min.js with the v2 changes, we actually don't need to continue maintaining a "latest" bundle at all. I think that doing this encourages folks to use it and opens up the possibility for breaking changes on our end to impact way more people that is strictly necessary, so I think we should not actually move foward with the previously-planned plotly-v2-latest.min.js plan and simply let folks use versioned bundles everywhere.