chore: Bump actions off Node.js 20

[dervoeti]

Description

We should probably merge stackabletech/actions#105 first and then bump the actions here as well.

We'll soon be affected by this (see the warnings in this PR run for example):

Node.js 20 actions are deprecated. The following actions are running on Node.js 20 and may not work as expected: anchore/sbom-action@0b82b0b, docker/login-action@5e57cd1, docker/setup-buildx-action@8d2750c. Actions will be forced to run with Node.js 24 by default starting June 2nd, 2026.

This bumps docker/login-action from v3.6.0 to v4.1.0 to get off Node.js 20 before the GitHub Actions runner deprecation.

I checked the changelog for breaking changes, didn't spot anything that would affect us.

Definition of Done Checklist

Note

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:

boil build <IMAGE> --image-version <RELEASE_VERSION> --strip-architecture --load
kind load docker-image <MANIFEST_URI> --name=<name-of-your-test-cluster>

See the output of boil to retrieve the image manifest URI for <MANIFEST_URI>.