[spec] Limit valid encodings of text/gemini to UTF-8

[Petite Abeille]

> On Dec 29, 2020, at 22:24, Peter Vernigorov <pitr.vern at gmail.com> wrote:
> 
> Looking at latest stats on
> gemini://gemini.bortzmeyer.org/software/lupa/stats.gmi it looks like
> UTF-8 (this includes unspecified charsets which per spec default to
> UTF-8) is used by 81% of pages, US-ASCII accounts for 17%.

The actual numbers are as follow:

• Unspecified: 39628
• us-ascii: 9995
• utf-8: 7090
( 56,713 total)

It's not clear if this pertain to the 36,477 text/gemini documents only, or the entire dataset (57,164 url vs. 56,713 encodings. 451 MIA).

Looking at the numbers I guess it covers the entire data set as there are more 'Unspecified' than 'text/gemini' to start with.

I'm not sure what these numbers mean at all, but they are not describing text/gemini.

Not sure why we would draw any conclusion from them in regards to  text/gemini.