update rb/stored-css to match javascript

Author: erik-krogh

ruby/ql/src/queries/security/cwe-079/StoredXSS.ql

@@ -18,5 +18,5 @@ import DataFlow::PathGraph
 
 from StoredXss::Configuration config, DataFlow::PathNode source, DataFlow::PathNode sink
 where config.hasFlowPath(source, sink)
-select sink.getNode(), source, sink, "Cross-site scripting vulnerability due to $@",
+select sink.getNode(), source, sink, "Stored cross-site scripting vulnerability due to $@.",
   source.getNode(), "stored value"