ci: use ubuntu-latest over deprecated ubuntu-20.04
#403
larponci.yml
on: pull_request
code-formatting
30s
ubuntu-latest-bootstrap
4m 11s
ubuntu-latest-shy-can-live-anywhere
4m 3s
ubuntu-latest-build
4m 33s
Matrix: sdl-branch-versions
Matrix: sdl-d-gamepad-branch-versions