Remove transaction from componentWillUpdate

It wasn't documented and I think the transaction is supposed to be internal.

src/core/ReactCompositeComponent.js

@@ -758,7 +758,7 @@ var ReactCompositeComponentMixin = {
     var prevState = this.state;
 
     if (this.componentWillUpdate) {
-      this.componentWillUpdate(nextProps, nextState, transaction);
+      this.componentWillUpdate(nextProps, nextState);
     }
 
     this.props = nextProps;