Replace ubuntu-20.04 with 22.04 in CI

- ubuntu-20.04 is no longer supported,
  ubuntu-latest is now 24.04

Author: mrbean-bremen

.github/workflows/ci.yml

@@ -4,7 +4,7 @@ on: [push, pull_request]
 
 jobs:
   build:
-    runs-on: ubuntu-20.04, ubuntu-latest, macos-latest
+    runs-on: [ubuntu-22.04, ubuntu-latest, macos-latest]
     strategy:
       matrix:
         python-version: ["3.8", "3.9", "3.10", "3.11", "3.12", "3.13"]