doc: fix initrd FAQ section
doc: fix initrd FAQ section

Signed-off-by: tidux <44f878afe53efc66b76772bd845eb65944ed8232@dorsal.tk>

firecracker-microvm/firecracker,firecracker-microvm/firecracker,firecracker-microvm/firecracker,firecracker-microvm/firecracker,firecracker-microvm/firecracker