chore(kafka): Remove kubectl

[sbernauer]

Description

Not needed anymore since stackabletech/kafka-operator#443.
We could have removed back than already, but waited for 24.11 explicitly just to be sure.

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

- [ ] Changes are OpenShift compatible
- [ ] All added packages (via microdnf or otherwise) have a comment on why they are added
- [ ] Things not downloaded from Red Hat repositories should be mirrored in the Stackable repository and downloaded from there
- [ ] All packages should have (if available) signatures/hashes verified
- [ ] Add an entry to the CHANGELOG.md file
- [ ] Integration tests ran successfully

TIP: Running integration tests with a new product image

The image can be built and uploaded to the kind cluster with the following commands:

bake --product <product> --image-version <stackable-image-version>
kind load docker-image <image-tagged-with-the-major-version> --name=<name-of-your-test-cluster>

See the output of bake to retrieve the image tag for <image-tagged-with-the-major-version>.

[nightkr]

Do we want to document somewhere for 24.11 that this is deprecated?

[sbernauer]

I'm happy to silently remove it, as only kafka-operator should be using it.
I just proposed to wait until the release is over, just in case some customer messes up his env and the product image being more recent than the operator image

[adwk67]

LGTM!
(built images locally, verified kubectl is no longer in the images, nightly tests all good).