Remove stackableVersion from ZookeeperCluster CRD

[Maleware]

Description

Fixing hardcoded stackableVersion: 23.7.0

as it broke integration tests on ARM and is not supposed to be used anymore as we have ImageSelection by operator version.

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

[Maleware]

That should be alright shouldn't it?

as we want to test with different product versions

- name: zookeeper
    values:
      - 3.8.3
  - name: zookeeper-latest
    values:
      - 3.9.2

[maltesander]

Go for what razvan suggested. We do not need to test with multiple zookeeper versions here.

[Maleware]

Done with https://github.com/stackabletech/druid-operator/pull/581/commits/dca1109ee215fcada30c368f0fd95502a1516481

[maltesander]

This one left (found by @razvan ) https://github.com/stackabletech/druid-operator/blob/23bd67cdd000e1d690679170703b6f797112637e/tests/templates/kuttl/oidc/40_druid.yaml.j2#L28 :)

[Maleware]

Done with https://github.com/stackabletech/druid-operator/pull/581/commits/ec6d225642b8f822e2a1cdc2abcfac50586acc59