Corrected Docker(shim) UNIX domain socket file

This page listed `/var/run/docker.sock` as the UNIX domain socket path for the Docker container runtime, but it's actually `/var/run/dockershim.sock`, as the kubelet documentation indicates as the default value for the `--container-runtime-endpoint` argument:

https://kubernetes.io/docs/reference/command-line-tools-reference/kubelet/

The socket file specified (`/var/run/docker.sock`) is where the Docker daemon listens for requests for the Docker API, not the CRI interface.

Author: diegonuevo

content/en/docs/setup/production-environment/tools/kubeadm/install-kubeadm.md

@@ -122,7 +122,7 @@ The following table lists container runtimes and their associated socket paths:
 {{< table caption = "Container runtimes and their socket paths" >}}
 | Runtime    | Path to Unix domain socket        |
 |------------|-----------------------------------|
-| Docker     | `/var/run/docker.sock`            |
+| Docker     | `/var/run/dockershim.sock`        |
 | containerd | `/run/containerd/containerd.sock` |
 | CRI-O      | `/var/run/crio/crio.sock`         |
 {{< /table >}}