bump kuberntes-client to latest kubernetes-client (6.12.0)

[adietish]

redhat-developer/intellij-kubernetes#726 in intellij-kubernetes requires a bump to a fixed kubernetes-client (6.12.0).

Depends on:

• refactor: bump kubernetes-client to 6.12.0 (#210) intellij-common#211
• chore(skip-release): Prepare for 1.9.4 intellij-common#220

[adietish]

6.11.0 did not fix fabric8io/kubernetes-client#5817: https://github.com/fabric8io/kubernetes-client/releases/tag/v6.11.0
Targeting 6.12.0 then.