Rename kustomization.yaml generated by flux2-sync

[suryapandian]

What this PR does / why we need it:

Renames kustomization.yaml to flux-kustomization.yaml and gitrepository.yaml to flux-gitrepository.yaml

We need this fix because kustomization.yaml by convention of kustomize refers to this.

Which issue this PR fixes

(optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged)

• fixes https://github.com/fluxcd-community/helm-charts/issues/105

Special notes for your reviewer:

Checklist

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

[suryapandian]

charts/flux2-sync/README.md got automatically updated when I ran helm-docs

[haarchri]

Can you Check DCO ? Then we can run E2E Checks

[suryapandian]

Can you Check DCO ? Then we can run E2E Checks

Done ✅