grains: Update Debian/Ubuntu releases in test cases
grains: Update Debian/Ubuntu releases in test cases

Update the OS grains test cases to use `/etc/os-release` data from still
supported Debian/Ubuntu releases.

Signed-off-by: Benjamin Drung <86a6db991ec5c1a96f98c92b98df9d547d7c8c84@ionos.com>

saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt