update available python versions (#349)

* update available python versions

* Python 3.11 requires the latest pybind

Author: philbucher

.github/workflows/ci.yml

@@ -120,7 +120,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.6", "3.7", "3.8", "3.9", "3.10"]
+        python-version: ["3.7", "3.8", "3.9", "3.10"]
         compiler: [GCC, ICC]
     timeout-minutes: 15