list the 'pinch' event in code comments

Has `'pinch'` been accidentally omitted from the in-code comments?

```javascript
if(scaleThreshold > inst.options.transformMinScale) {
    inst.trigger('pinch', ev);  // <<--- `pinch` event, HERE !
    inst.trigger('pinch' + (ev.scale < 1 ? 'in' : 'out'), ev);
}
```