[NFDIV-4080] Test using helm chart from git repository

[adamg-hmcts]

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Checklist

• [ ] commit messages are meaningful and follow good commit message guidelines
• [ ] README and other documentation has been updated / added (if needed)
• [ ] tests have been updated / new tests has been added (if needed)
• [ ] Does this PR introduce a breaking change

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apps/nfdiv/nfdiv-ccd-case-migration/nfdiv-ccd-case-migration.yaml

• Updated the chart field under spec.

  • Changed the chart from nfdiv-ccd-case-migration to ./stable/nfdiv-ccd-case-migration.
  • Updated the kind and name under sourceRef from HelmRepository to GitRepository and hmctspublic to hmcts-charts respectively.
  • Added a new field namespace with the value flux-system.
  • Set an interval of 1 minute.