change reference and link target from SPARQL12-QUERY to SPARQL12-CONCEPTS

Author: TallTed

spec/index.html

@@ -1080,7 +1080,7 @@ <h2>RDF Datasets</h2>
       can avoid interoperability issues by not ascribing importance to
       the presence or absence of empty named graphs.</p>
 
-    <p>Version 1.2 of the SPARQL Query Language [[SPARQL12-QUERY]] uses 
+    <p>SPARQL version 1.2 [[SPARQL12-CONCEPTS]] uses 
       <a data-cite="SPARQL12-QUERY#sparqlDataset">the same concept of an RDF Dataset</a>
       as RDF versions 1.1 and 1.2,
       in which the graph names of named graphs may be IRIs or blank nodes.