update Air Toxics Cancer Risk symbolization

[ericnost]

Change the legend/bins for Air Toxics Cancer Risk in Places: Other Environmental Data. Right now large areas are one color block so the map really doesn't give much information. Plus we could transform this into percentiles anyway and it might be more accessible. Regardless, we could show the raw data as more granulated bins (more like a heatmap)?

Some background: this is one the map layers that is still publicly available, so nothing about it has/should have changed. It's being served from whoever runs this https://services.arcgis.com/cJ9YHowT8TU7DUyn/ArcGIS/rest/services/ (some sort of EPA default ArcGIS server?)
To adjust the legend/bins, and use percentiles instead, I think we'd do the following:

• load into a GIS
• create a local copy
• calculate percentiles (if not already calculated)
• symbolize as needed
• publish to a new feature server
• get that link
• update config.js in the EJScreen code
• update layer url
• update renderer (use percentile renderer)