redhat: Fix macro for kernel-uki-virt flavor

When the versioned systemd dependency was dropped, the structure for the macro was accidentally broken, resulting in the error:

error: kernel.spec: line 1522: %endif with no %if

This change puts back the missing backslash that makes the macro evaluate properly again.

Fixes: be6000d0 ("Change the uki reqs for Fedora")

Signed-off-by: Neal Gompa ngompa@fedoraproject.org