simplify the where clause of rb/kernel-open

Author: erik-krogh

ruby/ql/src/queries/security/cwe-078/KernelOpen.ql

@@ -71,7 +71,7 @@ from
 where
   config.hasFlowPath(source, sink) and
   sourceNode = source.getNode() and
-  call.asExpr().getExpr().(MethodCall).getArgument(0) = sink.getNode().asExpr().getExpr()
+  call.getArgument(0) = sink.getNode()
 select sink.getNode(), source, sink,
   "This call to " + call.(Replacement).getFrom() + " depends on a . Replace it with " +
     call.(Replacement).getTo() + ".", source.getNode(), "user-provided value"