docs: remove reference to GCM doc from C2DM doc
docs: remove reference to GCM doc from C2DM doc

Change-Id: Ic044916487d56bab22e30b24392890b97acf9d44

xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base