Fixed copy/paste error in the .TaskDidCancel notification names value.

Source/NotificationNames.swift

@@ -25,5 +25,5 @@ import Foundation
 public struct NotificationNames {
     public static let TaskDidResume = "com.alamofire.task.did.resume"
     public static let TaskDidSuspend = "com.alamofire.task.did.suspend"
-    public static let TaskDidCancel = "com.alamofire.task.did.suspend"
+    public static let TaskDidCancel = "com.alamofire.task.did.cancel"
 }