CI: update 3.9 packages as they become available

[jreback]

we now have 3.9 support via conda-forge: #37039

we should periodically update the tested packages as they become available.

[jreback]

cc @fangchenli

[jreback]

I believe we could add most / all of the current 3.8 deps, e.g. we just added pytables and its good from conda-forge: https://github.com/pandas-dev/pandas/pull/38041/files