chore(kind): remove unused variable and rename file

[lukidzi]

Checklist prior to review

Config files always have suffix based onKIND_CLUSTER_NAME.

• Link to relevant issue as well as docs and UI issues -- fix: make kind/start fails with "No kind clusters found." (because cluster-kuma.yaml doesn't exist) #9131
• This will not break child repos: it doesn't hardcode values (.e.g "kumahq" as a image registry) and it will work on Windows, system specific functions like syscall.Mkfifo have equivalent implementation on the other OS --
• Tests (Unit test, E2E tests, manual test on universal and k8s) --
  • Don't forget ci/ labels to run additional/fewer tests
• Do you need to update UPGRADE.md? --
• Does it need to be backported according to the backporting policy? (this GH action will add "backport" label based on these file globs, if you want to prevent it from adding the "backport" label use no-backport-autolabel label) --

[michaelbeaumont]

IIRC the previous attempt broke CI #9026

[michaelbeaumont]

Also originally the problem comes from #8676

[lukidzi]

I see, the previous pr was adding -1 to each file configuration name. I think now I've renamed the file correctly + using the value provided in KIND_CLUSTER_NAME so I hope it should work. I am going to run full matrix.

[lahabana]

Sounds solid to me!