largest-series-product: Canonical data has non-standard error indicator

[Insti]

The canonical data for the largest-series-product exercise has an expected value of -1 for the error cases.

The canonical data documentation says

If an error is expected (because the input is invalid, or any other reason), the value at "expected" should be an object containing exactly one property, "error", whose value is a string.

Todo:

Update the largest-series-product canonical-data.json to use the correct error format.

See also: hamming canonical-data.json for another example of how to do things the right way.

[Insti]

Thanks @sdublish ❤️