ENH appveyor is ok list

[beckermr]

I've gone through the rest of the feedstocks that have appveyor.

The ones on this list currently use appveyor to build on master and have been worked on recently.

Everything else has been

• moved to azure
• uses appveyor on a version branch (e.g. python)
• uses appveyor on a PR branch that should not be there
• is a recipe that is 1.5 years to 4 years out of date

I have left these feedstocks off the list under the assumptions that

1. should they ever get updated (either in a branch on master, we would rerender and move to azure)
2. we can add any feedstock back later

Hopefully isl and libssh2 can be moved over to azure before this PR is merged.

cc @conda-forge/core for viz

here are my notes: https://hackmd.io/HSwAaR3ZTzSA70kSiPRwcg?edit

[beckermr]

OK @conda-forge/core I've inspected the builds of the remaining packages. I removed anything that was either not maintained or had a build error that didn't appear to me to be related to azure versus appveyor. This left just isl in the list. I saw that @isuruf is working on moving the build of that to azure. So I think we should leave this issue open until we know about isl and then make a decision.

[beckermr]

We moved isl due to hard work from @isuruf. I think we can just no longer support appveyor going forward. Closing!