fix(dracut-systemd): use `DRACUT_VERSION` instead of `VERSION`

[aafeijoo-suse]

VERSION can contain other values unrelated to the dracut version, which garbles the output.

E.g.:

openSUSE Tumbleweed:

Oct 10 14:17:58 localhost dracut-cmdline[236]: dracut-dracut-059+suse.501.gc44a365d-1.1

Fedora Rawhide:

Oct 10 14:00:42 fedora dracut-cmdline[300]: dracut-40 (Workstation Edition Prerelease) dracut-059-12.fc39

Arch Linux:

Oct 10 14:31:59 localhost dracut-cmdline[159]: dracut-dracut-059

Checklist

• [X] I have tested it locally
• [ ] I have reviewed and updated any documentation if relevant
• [ ] I am providing new code and test(s) for it

[stale[bot]]

This issue is being marked as stale because it has not had any recent activity. It will be closed if no further activity occurs. If this is still an issue in the latest release of Dracut and you would like to keep it open please comment on this issue within the next 7 days. Thank you for your contributions.