corrections to validation status upload to minio

[douglowe]

Removing the data_path named variable from the ValidationSettings call because this variable was renamed rocrate_uri in commit crs4/rocrate-validator@f62a8ae

[douglowe]

I've also corrected the calculation of the length of the string object that is uploaded - previously we cut the string short because the length was taken of the dictionary, not the string.

[douglowe]

And I've (finally) realised that the validation_status object passed to this function is a string.

The original string is in pretty JSON format (with line endings and indents). So I've retained the json.dumps function, but within this I use a json_loads function to turn this pretty string into a dictionary, which is then turned back into a less pretty, but infinitely more useful, string.