Namespace prefix sfn: should become sparql:

The current SPARQL 1.2 Query Language draft mentions prefix sfn: for http://www.w3.org/ns/sparql#

Elsewhere, the prefix is used as sparql: and in the SHACL 1.2 spec we'll use that too.

It seems that the document currently doesn't even use sfn: so maybe it can just be deleted?


