chore: update python versions used

Updated in different places at different times.
Make consistent for now.

Refs: pypa@675acbb
Refs: pypa@90a1d07

Signed-off-by: Mike Fiedler <miketheman@gmail.com>

Author: miketheman

.github/workflows/test.yml

@@ -28,7 +28,7 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v4
         with:
-          python-version: 3.9
+          python-version: "3.11"
           cache: 'pip'
           cache-dependency-path: 'requirements.txt'
 

source/contribute.rst

@@ -131,9 +131,9 @@ need:
 
       python -m pip install --user nox
 
-2. Python 3.8. Our build scripts are usually tested with Python 3.8 only.
+2. Python 3.11. Our build scripts are usually tested with Python 3.11 only.
    See the :doc:`Hitchhiker's Guide to Python installation instructions <python-guide:starting/installation>`
-   to install Python 3.8 on your operating system.
+   to install Python 3.11 on your operating system.
 
 To build the guide, run the following shell command in the project's root folder: