doc: use "Calls" over "Executes" for consistency

"Calls" is used frequently throughout the docs except for this line.
Use "Calls" over "Executes" to make it consistent.

PR-URL: https://github.com/nodejs/node/pull/2800
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>

doc/api/events.markdown

@@ -132,7 +132,7 @@ Returns a copy of the array of listeners for the specified event.
 
 ### emitter.emit(event[, arg1][, arg2][, ...])
 
-Executes each of the listeners in order with the supplied arguments.
+Calls each of the listeners in order with the supplied arguments.
 
 Returns `true` if event had listeners, `false` otherwise.