Hazelcast Docker version specified in documentation outdated

The example Docker commands refer to Hazelcast `5.3`, even though newer versions are available.

It would be simpler if they used `latest` instead, to avoid needing to update in future - but then older documentation (e.g. [this "getting started"](https://hazelcast.readthedocs.io/en/v5.2.0/getting_started.html#setting-up-a-hazelcast-cluster) page for `5.1`) might be broken if the older client isn't compatible with `latest`.

So for that reason I think just updating the version is safest.