Input format in revsort example is a broken link

In the revsort example, the input file [format](https://github.com/common-workflow-language/cwlprov/blob/ce3f469745f4c8a2c029f872d522a4c57fba947b/examples/revsort-run-1/workflow/packed.cwl#L16) is https://www.iana.org/assignments/media-types/text/plain, but that page does not exist. I'm not even sure this is a problem: is that supposed to lead to an actual web page? Or is there a reference doc stating that's the correct URI? Would https://www.rfc-editor.org/rfc/rfc2046.html#section-4.1.3 be a viable URL alternative?