flux2-notification: fix provider template

[yurymuski]

Which issue this PR fixes

fix: #178

Special notes for your reviewer:

Checklist

• [x] DCO signed
• [x] Chart Version bumped
• [x] helm-docs are updated
• [x] Helm chart is tested
• [x] Update artifacthub.io/changes in Chart.yaml
• [x] Run make reviewable

[yurymuski]

seems you are using old version of helm-unit tests, new one does not know about --helm3 flag, and requires indentation changes

pushed commit w/o indentation changes

[stefanprodan]

@yurymuski could you please update helm-test in a different PR?

[yurymuski]

@stefanprodan sure, I can update tests, will add it todo list :)