GH Actions: Upgraded Python, setup-python, checkout

Signed-off-by: Ole Herman Schumacher Elgesem <[email protected]>

.github/workflows/markdowner.yml

@@ -5,18 +5,17 @@ on:
     branches: [ master ]
   pull_request:
     branches: [ master ]
-    workflow_dispatch:
 
 jobs:
   check:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-24.04
     steps:
     - name: Checks-out repository
-      uses: actions/checkout@v2
-    - name: Set up Python 3.7
-      uses: actions/setup-python@v2
+      uses: actions/checkout@v4
+    - name: Set up Python 3.12
+      uses: actions/setup-python@v5
       with:
-        python-version: "3.7"
+        python-version: "3.12"
     - name: Run markdowner.py to (hopefully not) edit markdown files
       run: |
         find . -name '*.markdown' -type f -exec python3 .github/workflows/markdowner.py {} all \; | tee output.log