update to landsat-8 collection-2

[scottyhq]

The original version of this demo was created a number of years ago using landsat8 data on AWS that was managed by Planet. That dataset is deprecated and will disappear on July 1 2021 according to
https://registry.opendata.aws/landsat-8/

An ongoing collection of satellite imagery of all land on Earth produced by the Landsat 8 satellite.Note this dataset is deprecated in favor of the USGS cloud access mechanism

This demo should really be using collection-2 landsat (released dec 2020)
https://www.usgs.gov/news/usgs-releases-most-advanced-landsat-archive-date
https://www.usgs.gov/core-science-systems/nli/landsat/landsat-commercial-cloud-data-access

Or Harmonized-L8 Sentinel-2... from NASA's LPDAAC
https://lpdaac.usgs.gov/data/get-started-data/collection-overview/missions/harmonized-landsat-sentinel-2-hls-overview/

[scottyhq]

Also, might want to use stackstac instead of intake-stac https://github.com/gjoseph92/stackstac

@rmg55 has a great example here https://gist.github.com/rmg55/b144cb273d9ccfdf979e9843fdf5e651