ci: use ubuntu v24 for GNU tests workflow

[cakebaker]

This PR bumps ubuntu from 22.04 to 24.04 in the GNU tests workflow and installs the libselinux1-dev package to fix the build issue mentioned in #6742 (comment)

[github-actions]

GNU testsuite comparison:

GNU test failed: tests/ls/stat-free-symlinks. tests/ls/stat-free-symlinks is passing on 'main'. Maybe you have to rebase?
GNU test failed: tests/timeout/timeout. tests/timeout/timeout is passing on 'main'. Maybe you have to rebase?
Congrats! The gnu test tests/rm/rm2 is no longer failing!

[github-actions]

GNU testsuite comparison:

GNU test failed: tests/ls/stat-free-symlinks. tests/ls/stat-free-symlinks is passing on 'main'. Maybe you have to rebase?
GNU test failed: tests/timeout/timeout. tests/timeout/timeout is passing on 'main'. Maybe you have to rebase?
Congrats! The gnu test tests/rm/rm2 is no longer failing!