docker{,-rootful}.yaml: Enable the containerd image store by default

To support building multi-platform images.
Use `--set .param.containerdSnapshotter=false` flag to disable it.

#3858 (comment)
> https://docs.docker.com/desktop/features/containerd/
> > The containerd image store is enabled by default in Docker Desktop version 4.34 and later, but only for clean installs or if you perform a factory reset.
>
> 4.34 was released on 2024-08-29
> https://docs.docker.com/desktop/release-notes/#4340

Signed-off-by: Norio Nomura <[email protected]>

Author: norio-nomura

templates/docker-rootful.yaml

@@ -68,4 +68,4 @@ message: |
   docker run hello-world
   ------
 param:
-  containerdSnapshotter: false
+  containerdSnapshotter: true

templates/docker.yaml

@@ -75,4 +75,4 @@ message: |
   docker run hello-world
   ------
 param:
-  containerdSnapshotter: false
+  containerdSnapshotter: true