docs: Fix getting started guide to use Postgres and TLS

[sbernauer]

Description

1. We should never encourage derby! After reboot of the coordinator (24h at max), your Druid will loose all data.
2. Let's not disable TLS

[...]
Awaiting Druid rollout finish
Waiting for 1 pods to be ready...
partitioned roll out complete: 1 new pods have been updated...
partitioned roll out complete: 1 new pods have been updated...
partitioned roll out complete: 1 new pods have been updated...
partitioned roll out complete: 1 new pods have been updated...
partitioned roll out complete: 1 new pods have been updated...
Starting port-forwarding of port 9088
Submitting job
Task still running...
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Task finished successfully!
Segments still loading...
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Querying data...
Query result is as expected!

Definition of Done Checklist

• Not all of these items are applicable to all PRs, the author should update this template to only leave the boxes in that are relevant
• Please make sure all these things are done and tick the boxes

# Author
- [ ] Changes are OpenShift compatible
- [ ] CRD changes approved
- [ ] CRD documentation for all fields, following the [style guide](https://docs.stackable.tech/home/nightly/contributor/docs/style-guide).
- [ ] Helm chart can be installed and deployed operator works
- [ ] Integration tests passed (for non trivial changes)
- [ ] Changes need to be "offline" compatible

# Reviewer
- [ ] Code contains useful comments
- [ ] Code contains useful logging statements
- [ ] (Integration-)Test cases added
- [ ] Documentation added or updated. Follows the [style guide](https://docs.stackable.tech/home/nightly/contributor/docs/style-guide).
- [ ] Changelog updated
- [ ] Cargo.toml only contains references to git tags (not specific commits or branches)

# Acceptance
- [ ] Feature Tracker has been updated
- [ ] Proper release label has been added
- [ ] [Roadmap](https://github.com/orgs/stackabletech/projects/25/views/1) has been updated

[razvan]

Works nicely!