docker-outside-of-docker feature wrongly update container entrypoint

in a dev container with **compose.yml** that use docker-outside-of docker feature [it updates the main entrypoint](https://github.com/devcontainers/features/blob/main/src/docker-outside-of-docker/devcontainer-feature.json#L44) which is not the expected result

with feature enabled
```sh
docker inspect --format='{{.Config.Entrypoint}}'
[
[/bin/sh -c echo Container started
trap "exit 0" 15
/usr/local/share/docker-init.sh
exec "$@"
while sleep 1 & wait $!; do :; done - /usr/local/share/docker-init.sh
]
```

without feature enabled
```sh
docker inspect --format='{{.Config.Entrypoint}}'
[
[/bin/sh -c echo Container started
trap "exit 0" 15

exec "$@"
while sleep 1 & wait $!; do :; done - /usr/local/share/docker-init.sh
]
```

**Solution**
use the `postStartCommand` instead

**Additional info**
maybe #483 it's related