Fix argument passing to Meteor.Collection.update.

This only affects the overridden `Meteor.Collection.update`; no fixes are needed for insert or remove. This is because `insert` and `remove` only take 1 or 2 arguments, and passing a `callback` to them without a `selector` wouldn't make any sense anyway. However, not passing `options` to `update` (and terminating the invocation with a callback) is rather common.