[spec] <URL> is a UTF-8 erratum

[Petite Abeille]

The spec says, as of v0.14.3, November 29th 2020, under # 2 Gemini requests:

<URL> is a UTF-8 encoded absolute URL, including a scheme, of maximum length 1024 bytes. 

This is wrong.

What's wrong is URL. It should read IRI instead, to make it consistent with UTF-8. An URL cannot be UTF-8, while an IRI can. As UTF-8 precedes URL in the sentence, UTF-8 has to take precedence.

I suggest the following correction:

<URL> is a UTF-8 encoded absolute IRI, including a scheme, of maximum length 4,096* bytes. 

* Note the increase in size, to compensate for the consistent use of UTF-8 encoding.

To avoid confusion further down the document (inconsistent use of URL vs. URI. vs IRI), I would suggest to systematically refer to IRI for all of them.

Which gives us:

<IRI> is a UTF-8 encoded absolute IRI, including a scheme, of maximum length 4,096 bytes.