[PATCH 2/2] sbat: Also bump latest for grub,4 (and to todays date) Back in January we decided to bump the SBAT level for the shim CVE without bumping the grub level for the previous NTFS issues - CVE-2023-4692 CVE-2023-4693 - as not every vendor was signing the ntfs module.
Catch up on this revocation to ensure it doesn't get lost. Doing so also allows us to remove the grub.debian,4 revocation as this happened before grub,4 and hence is obsolete.
Also bump the date of the sbat variable to today's. Don't copy the April 5 one to a previous selection, as it wasn't shipped to anyone.
