[web/views/rdf] Take the second element of XY equivalent for non final relation
When given a Yams snippet of the form `<etype> <rtype>` ``xy.xeq()`` will
return the XML snippet equivalent to this relation in the form of a tuple
`(subject, rtype, object)` so ``item`` will always be a tuple here.
In fact, the correct code appears just a few lines above (around line 88) for
final relations so I guess this is a copy-paste mistake.
Closes #4745929.