Fix python test environment setup. (#844)

* Fix ubuntu version to 22.04 in python test environment setup.

* Try using python 3.9, but keeping latest ubuntu version.

* Try keeping latest ubunut and python 3.8, but change to newer checkout/setup verions.

Author: LeanderFischer

.github/workflows/pythonpackage.yml

@@ -18,9 +18,9 @@ jobs:
         python-version: ['3.8', '3.10']
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
     - name: Set up Python ${{ matrix.python-version }}
-      uses: actions/setup-python@v1
+      uses: actions/setup-python@v5
       with:
         python-version: ${{ matrix.python-version }}
     - name: Install dependencies