Simplify grub_efi_path on redhat family

Remains backwards-compatible with supported distros, and we don't
have to look for openeuler or oraclelinux or any other EL variant.

manifests/tftp/netboot.pp

@@ -28,10 +28,7 @@
 
   case $grub_installation_type {
     'redhat': {
-      $grub_efi_path = $facts['os']['name'] ? {
-        /Fedora|CentOS|AlmaLinux|Rocky/ => downcase($facts['os']['name']),
-        default         => 'redhat',
-      }
+      $grub_efi_path = downcase($facts['os']['name'])
 
       file { "${root}/grub2/grubx64.efi":
         ensure  => file,