Fix javadoc

Change-Id: Ie98dd00f41add876f3740f5d37781a10c6bd41fe

Author: Romain Guy

core/java/android/os/AsyncTask.java

@@ -110,7 +110,7 @@
  * <h2>The 4 steps</h2>
  * <p>When an asynchronous task is executed, the task goes through 4 steps:</p>
  * <ol>
- *     <li>{@link #onPreExecute()}, invoked on the UI thread immediately after the task
+ *     <li>{@link #onPreExecute()}, invoked on the UI thread before the task
  *     is executed. This step is normally used to setup the task, for instance by
  *     showing a progress bar in the user interface.</li>
  *     <li>{@link #doInBackground}, invoked on the background thread