Fix chart testing configuration per individual Github action pipeline

[RafalKorepta]

--chart-dirs was not working as I would think.

REF:
https://github.com/redpanda-data/helm-charts/actions/runs/5678517663/job/15388898267#step:7:14

$ ct lint --config .github/ct.yaml --github-groups --chart-dirs=charts/kminion
Linting charts...
>>> helm version --template {{ .Version }}
>>> git rev-parse --is-inside-work-tree
>>> git rev-parse --verify main
>>> git merge-base origin/main HEAD
>>> git diff --find-renames --name-only aba186603a055[2](https://github.com/redpanda-data/helm-charts/actions/runs/5678517663/job/15388898267#step:7:2)a0d65d8df9d8c4a[3](https://github.com/redpanda-data/helm-charts/actions/runs/5678517663/job/15388898267#step:7:3)8cde70b9[5](https://github.com/redpanda-data/helm-charts/actions/runs/5678517663/job/15388898267#step:7:5)3 -- charts/kminion
Directory "charts/kminion/ci" is not a valid chart directory. Skipping...
Test Results
  No chart changes detected.
All charts linted successfully

https://github.com/redpanda-data/helm-charts/pull/616/files

[alejandroEsc]

lgtm