Renumbered rdf:List stress test user story

In the user stories page
https://www.w3.org/2014/data-shapes/wiki/User_Stories#S24:_Open_Content_Model
 there was a problem with the layout/numbering in the S20 & S21 range: a
story for rdf:List stress test had been added, but it came out (possibly in
the copy from the original pirate pad) as text embedded in the S20 story,
rather than being the intended next story S21. Meanwhile, other stories
have been added using S21, S22 ... S25.

I have separated out that rdf:List stress test story as a new entry S26.. If
there were any references to it elsewhere in email threads or the wiki
pages under the S21 number, it currently does not have that number.

Nick.