chore: use public repository metadata

[Soengkit]

Summary

• Update package.json#repository.url from the SSH GitHub endpoint to the public HTTPS form.
• Keep the repository metadata pointing at the same upstream repository.

Validation

• Checked the current npm metadata for @defra/hapi-gapi@2.1.8.
• Parsed package.json and asserted repository.url === "git+https://github.com/DEFRA/hapi-gapi.git".
• git diff --check
• git ls-remote https://github.com/DEFRA/hapi-gapi.git HEAD