Allow REQUEST_NOT_SUPPORTED when requesting data throttling from modem.

Test: make
Bug: 173806949
Change-Id: Icbf1febdc489e8b8cea91fcc4a149afafb01b1b9
diff --git a/radio/1.6/IRadioResponse.hal b/radio/1.6/IRadioResponse.hal
index d65c6d0..883711c 100644
--- a/radio/1.6/IRadioResponse.hal
+++ b/radio/1.6/IRadioResponse.hal
@@ -342,6 +342,7 @@
      *  RadioError:RADIO_NOT_AVAILABLE
      *  RadioError:MODEM_ERR
      *  RadioError:INVALID_ARGUMENTS
+     *  RadioError:REQUEST_NOT_SUPPORTED
      */
     oneway setDataThrottlingResponse(RadioResponseInfo info);