CI: test on ubuntu 22.04 or 24.04

20.04 was removed.

.github/workflows/ci.yml

@@ -47,7 +47,7 @@ jobs:
       fail-fast: false
       matrix:
         include:
-            - os: ubuntu-20.04
+            - os: ubuntu-22.04
               python-version: '3.9'
               toxenv: py39-fuse2
             - os: ubuntu-22.04