Use Python 3.12 in the GitHub Actions workflow for the Fluent linter

The current stable version of Python is Python 3.12, see
https://www.python.org/downloads, so we should switch to that since
Python 3.10 is older and only receives security updates.

.github/workflows/fluent_linter.yml

@@ -27,10 +27,10 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v4
 
-      - name: Use Python 3.10
+      - name: Use Python 3.12
         uses: actions/setup-python@v4
         with:
-          python-version: '3.10'
+          python-version: '3.12'
           cache: 'pip'
 
       - name: Install Fluent dependencies