Cleanup 2nd param to ReactEventEmitter.ensureListening

It was removed, so these callsites aren't actually doing anything.

src/core/ReactEventEmitter.js

@@ -244,7 +244,7 @@ var ReactEventEmitter = {
 
   /**
    * React references `ReactEventTopLevelCallback` using this property in order
-   * to allow dependency injection via `ensureListening`.
+   * to allow dependency injection.
    */
   TopLevelCallbackCreator: null,
 

src/core/__tests__/ReactEventEmitter-test.js

@@ -39,7 +39,6 @@ var ReactMount = require('ReactMount');
 var getID = ReactMount.getID;
 var setID = ReactMount.setID;
 var ReactEventEmitter;
-var ReactEventTopLevelCallback;
 var ReactTestUtils;
 var TapEventPlugin;
 
@@ -94,10 +93,9 @@ describe('ReactEventEmitter', function() {
     setID = ReactMount.setID;
     ReactEventEmitter = require('ReactEventEmitter');
     ReactTestUtils = require('ReactTestUtils');
-    ReactEventTopLevelCallback = require('ReactEventTopLevelCallback');
     idCallOrder = [];
     tapMoveThreshold = TapEventPlugin.tapMoveThreshold;
-    ReactEventEmitter.ensureListening(false, ReactEventTopLevelCallback);
+    ReactEventEmitter.ensureListening(false);
     EventPluginHub.injection.injectEventPluginsByName({
       TapEventPlugin: TapEventPlugin
     });

src/eventPlugins/__tests__/AnalyticsEventPlugin-test.js

@@ -27,7 +27,6 @@ describe('AnalyticsEventPlugin', function() {
   var EventPluginRegistry;
   var React;
   var ReactEventEmitter;
-  var ReactEventTopLevelCallback;
   var ReactTestUtils;
 
   var DefaultEventPluginOrder;
@@ -42,7 +41,6 @@ describe('AnalyticsEventPlugin', function() {
     EventPluginRegistry = require('EventPluginRegistry');
     React = require('React');
     ReactEventEmitter = require('ReactEventEmitter');
-    ReactEventTopLevelCallback = require('ReactEventTopLevelCallback');
     ReactTestUtils = require('ReactTestUtils');
 
     EventPluginRegistry._resetEventPlugins();
@@ -63,7 +61,7 @@ describe('AnalyticsEventPlugin', function() {
       'ChangeEventPlugin': ChangeEventPlugin
     });
 
-    ReactEventEmitter.ensureListening(false, ReactEventTopLevelCallback);
+    ReactEventEmitter.ensureListening(false);
   });
 
   it('should count events correctly', function() {