kubelet-upgrade-doc: Update the image tag command
This command replaces the usage of `grep` sub-shell by using `sed`'s
matching facility.
@@ -51,7 +51,7 @@ Run the following commands:
```bash
export latest_kube=<latest kubernetes version e.g. v1.18.0>
-sudo sed -i "s|$(grep -i kubelet_image_tag /etc/kubernetes/kubelet.env)|KUBELET_IMAGE_TAG=${latest_kube}|g" /etc/kubernetes/kubelet.env
+sudo sed -i "s|.*KUBELET_IMAGE_TAG.*|KUBELET_IMAGE_TAG=${latest_kube}|g" /etc/kubernetes/kubelet.env
sudo systemctl restart kubelet
sudo journalctl -fu kubelet
```
