ci: update ubuntu and action versions

Author: vsergeev

.github/workflows/tests.yml

@@ -20,11 +20,11 @@ jobs:
           - python-version: "pypy2.7"
             check-types: false
 
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-24.04
     container: ${{ matrix.container }}
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
 
     - name: Set up Python ${{ matrix.python-version }}
       if: ${{ matrix.python-version != '2.7' }}