fix: set grub timeout to 5s and remove load_video for RHEL-family

- Set timeout=5 so users can interrupt boot to edit grub entries
- Remove load_video which fails with 'can't find command' error in
  minimal grub environment and is unnecessary for serial console VMs

Author: Raboo

grub_common.go

@@ -141,14 +141,13 @@ func (g *grubCommon) mkconfigRhel(ctx context.Context) error {
 
 	cfg := fmt.Sprintf(`# Generated by d2vm
 set default="0"
-set timeout=0
+set timeout=5
 
 insmod part_msdos
 insmod fat
 search --no-floppy --label --set=root boot
 
 menuentry 'Rocky Linux %s' --class gnu-linux --class gnu --class os {
-    load_video
     insmod gzio
     linux /%s root=LABEL=rootfs ro net.ifnames=0 rootfstype=ext4 console=tty0 console=ttyS0,115200n8
     initrd /%s