Update GitHub Actions to use Ubuntu 24.04 and latest actions

Author: constantinius

.github/workflows/test.yaml

@@ -4,13 +4,13 @@ on: [ push, pull_request ]
 
 jobs:
   test:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-24.04
     strategy:
       matrix:
-        python-version: ['3.6', '3.7', '3.8', '3.9', '3.10', '3.11', '3.12']
+        python-version: ['3.8', '3.9', '3.10', '3.11', '3.12']
     steps:
-    - uses: actions/checkout@v2
-    - uses: actions/setup-python@v2
+    - uses: actions/checkout@v5
+    - uses: actions/setup-python@v6
       name: Setup Python ${{ matrix.python-version }}
       with:
         python-version: ${{ matrix.python-version }}