Use make-container serve by default

The switch from:
$ make docker-serve

to:
$ make container-serve

is far enough in the past that everyone should have a current Makefile.

Also highlight the command to fetch and use submodules.

content/en/docs/contribute/generate-ref-docs/kubectl.md

@@ -230,11 +230,9 @@ Build the Kubernetes documentation in your local `<web-base>`.
 
 ```shell
 cd <web-base>
-make docker-serve
+git submodule update --init --recursive --depth 1 # if not already done
+make container-serve
 ```
-{{< note >}}
-The use of `make docker-serve` is deprecated. Please use `make container-serve` instead.
-{{< /note >}}
 
 View the [local preview](https://localhost:1313/docs/reference/generated/kubectl/kubectl-commands/).
 

content/en/docs/contribute/generate-ref-docs/kubernetes-api.md

@@ -182,13 +182,10 @@ Verify the [local preview](http://localhost:1313/docs/reference/generated/kubern
 
 ```shell
 cd <web-base>
-make docker-serve
+git submodule update --init --recursive --depth 1 # if not already done
+make container-serve
 ```
 
-{{< note >}}
-The use of `make docker-serve` is deprecated. Please use `make container-serve` instead.
-{{< /note >}}
-
 ## Commit the changes
 
 In `<web-base>` run `git add` and `git commit` to commit the change.