biblio.sgml dead link

On master, doc/src/sgml/biblio.sgml  has a biblioentry for a pdf from ISO:

"Information technology — Database languages — SQL Technical Reports —
Part SQL Notation support 6: (JSON) for JavaScript Object"

That pdf was a 2017 edition but the url now points to .zip that no 
longer exists.

The replacement is a ~200 euro pdf (2021).  I'd be thankful if someone 
would send the pdf to me; maybe I can update my JSON tests.

And we should remove that entry from the bibliography (or have it point 
to the new page [1]).


Erik Rijkers


[1] https://www.iso.org/standard/78937.html