Remove extraneous assert

Author: petehunt

src/event/EventPluginHub.js

@@ -154,10 +154,6 @@ var EventPluginHub = {
  * @param {?function} listener The callback to store.
  */
  putListener: function(id, registrationName, listener) {
- invariant(
- ExecutionEnvironment.canUseDOM,
- 'Cannot call putListener() in a non-DOM environment.'
- );
  invariant(
  !listener || typeof listener === 'function',
  'Expected %s listener to be a function, instead got type %s',