update the CI (#140)

* use python 3.9 for upstream-dev [skip-ci] [test-upstream]

* add python=3.10

* revert the addition of python=3.10

Apparently, just like conda the setup-python action also assumes
single digit minor versions.

Author: keewis

.github/workflows/nightly.yml

@@ -43,7 +43,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: [3.8]
+        python-version: [3.9]
 
     outputs:
       artifacts_availability: ${{ steps.status.outputs.ARTIFACTS_AVAILABLE }}