Merge pull request firecracker-microvm#544 from Kern--/getting-started-rootfs

Remove unneeded rootfs prerequisite from getting-started.md

Author: Kern--

docs/getting-started.md

@@ -38,9 +38,6 @@ You need to have the following things in order to use firecracker-containerd:
 
   </details>
 * git
-* A root filesystem image (you can use the one
-  [described here](https://github.com/firecracker-microvm/firecracker/blob/main/docs/getting-started.md#running-firecracker)
-  as `hello-rootfs.ext4`).
 * A recent installation of [Docker CE](https://docker.com).
 * Go 1.13 or later, which you can download from [here](https://golang.org/dl/).