update python versions for tests

conform to versions available in  https://raw.githubusercontent.com/actions/python-versions/main/versions-manifest.json
selected the most recent at date of commit

Author: olisol1

.github/workflows/ci.yml

@@ -45,7 +45,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        pyver: ["3.6", "3.7", "3.8", "3.9", "3.10"]
+        pyver: ["3.6.15", "3.7.15", "3.8.16", "3.9.16", "3.10.10"]
       fail-fast: true
     steps:
       - name: Install deps