Use style option in vector layer examples

Providing a styleFunction option still works because the layer property is still named styleFunction.

examples/synthetic-points.js

@@ -46,7 +46,7 @@ var vectorSource = new ol.source.Vector({
 });
 var vector = new ol.layer.Vector({
   source: vectorSource,
-  styleFunction: function(feature, resolution) {
+  style: function(feature, resolution) {
     return styles[feature.get('size')];
   }
 });