Updated removeActiveAdmin documentation

Bug: 13176294
Change-Id: I0554c2c9a1f4aaa4283474ab7810678004985a2f
diff --git a/core/java/android/app/admin/DevicePolicyManager.java b/core/java/android/app/admin/DevicePolicyManager.java
index d26e429..8890335 100644
--- a/core/java/android/app/admin/DevicePolicyManager.java
+++ b/core/java/android/app/admin/DevicePolicyManager.java
@@ -1048,6 +1048,9 @@
      * by the application that owns the administration component; if you
      * try to remove someone else's component, a security exception will be
      * thrown.
+     *
+     * <p>Note that the operation is not synchronous and the admin might still be active (as
+     * indicated by {@link #getActiveAdmins()}) by the time this method returns.
      */
     public void removeActiveAdmin(@NonNull ComponentName admin) {
         if (mService != null) {