In the grub2 element the grub2-efi-x64-modules package
is missing in the centos 9 section, this cause a failure
because grub2 cannot find the neccecary files when
installing the bootloader on EFI systems.
It seems grub2-efi-x64-modules was not included in release
9, this is likely why the block was added initially without
this package. Since it is now there, the Centos 9 specific
block is no longer needed.
Removing the rhel 8 block as well, as it is identical to the
family "redhat" block i.e it is redundant.
Closes-Bug: #1957169
Change-Id: Ia6b0ecf0cd15fb23c6740543940ee513a8602afe
