docs: remove reference to GCM doc from C2DM doc

Change-Id: Ic044916487d56bab22e30b24392890b97acf9d44
diff --git a/docs/html/google/gcm/c2dm.jd b/docs/html/google/gcm/c2dm.jd
index fc95c2b..6ae7c1a 100644
--- a/docs/html/google/gcm/c2dm.jd
+++ b/docs/html/google/gcm/c2dm.jd
@@ -75,7 +75,6 @@
 <dt><strong>Canonical registration ID</strong></dt>
 <dd>There may be situations where the server ends up with 2 registration IDs for the same device. If the GCM response contains a registration ID, simply replace the registration ID you have with the one provided. With this feature your application doesn't need to send the device ID to your server anymore. For more information, see <a href="adv.html#canonical">Advanced Topics</a>.</dd>
-<p>GCM also provides client and server <a href="{@docRoot}reference/com/google/android/gcm/package-summary.html">helper libraries</a> to make writing your code easier.</p>
 <h3 id="interop">Relationship between C2DM and GCM</h3>