Doc change: add notes for ndk r4b.

Change-Id: Idf4e4d2ac2ed9c30b3afe258546861084f3f20aa
diff --git a/docs/html/sdk/android-2.1.jd b/docs/html/sdk/android-2.1.jd
index 7490bae..cd48a72 100644
--- a/docs/html/sdk/android-2.1.jd
+++ b/docs/html/sdk/android-2.1.jd
@@ -139,7 +139,7 @@
 
 <div class="toggleable closed">
   <a href="#" onclick="return toggleDiv(this)">
-        <img src="{@docRoot}assets/images/triangle-opened.png" class="toggle-img" height="9px" width="9px" />
+        <img src="{@docRoot}assets/images/triangle-closed.png" class="toggle-img" height="9px" width="9px" />
         Android 2.1, Revision 1</a> <em>(January 2010)</em></a>
   <div class="toggleme">
 <dl>