fix: change labels and servicename of core to get upgrade to work

[hamza-m-masood]

Which problem does the PR fix?

Without this change the helm upgrade from 8.7 will not work with the following error:

The StatefulSet "camunda-zeebe" is invalid: spec: Forbidden: updates to statefulset spec for fields other than 'replicas', 'ordinals', 'template', 'updateStrategy', 'persistentVolumeClaimRetentionPolicy' and 'minReadySeconds' are forbidden

What's in this PR?

Checklist

Please make sure to follow our Contributing Guide.

Before opening the PR:

• In the repo's root dir, run make go.update-golden-only.
• There is no other open pull request for the same update/change.
• Tests for charts are added (if needed).
• In-repo documentation are updated (if needed).

After opening the PR:

• Did you sign our CLA (Contributor License Agreement)? It will show once you open the PR.
• Did all checks/tests pass in the PR?

[jessesimpson36]

This is outdated. and I am not even sure it's accurate anymore given that we have 8.7 -> 8.8 minor version integration tests passing currently.