Remove stray reference to rangeoverflow in example comment.

examples/timeline/items/pointItems.html

@@ -49,7 +49,7 @@
 
   var options = {
     // Set global item type. Type can also be specified for items individually
-    // Available types: 'box' (default), 'point', 'range', 'rangeoverflow'
+    // Available types: 'box' (default), 'point', 'range'
     type: 'point',
     showMajorLabels: false
   };