ci: unbreak pdd installation by updating Ubuntu image to bring newer …

…Ruby

> nokogiri requires Ruby version >= 3.0, < 3.4.dev. The current ruby version is 2.7.0.0

So, let's use Ubuntu 22.04 that has Ruby 3.0.2p107

Part of #1657

Fix #1654

.github/workflows/todos-extract-from-code.yml

@@ -29,7 +29,7 @@ jobs:
   extract-pdd-puzzles:
     name: Extract todos from code
     # https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#jobsjob_idruns-on
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     steps:
       - name: Clone source code
         uses: actions/[email protected] # https://github.com/actions/checkout