Cannot Install ISIS >8.0.3

It [appears as though ISIS](https://github.com/DOI-USGS/ISIS3/blob/dev/CHANGELOG.md) versions 8.1.0 and 8.2.0 have been released, but so far I have been unable to install it. Running `conda search -f isis` and `conda search -c usgs-astrogeology -f isis` only reveals up through version 8.0.3. I thought this was a "me thing" with 8.1.0, but now that 8.2.0 appears to be out and I still can't update to any version >8.0.3, I wanted to post this. Perhaps it is still a "me thing?"

Start with CHANGELOG.md and reproduce the reported `conda search -f isis` and `conda search -c usgs-astrogeology -f isis` commands. Compare the released versions with the packages exposed by those channels; done means versions newer than 8.0.3 can be found and installed, or the issue explains why they are unavailable.

Written by the indexing model from the issue text.