Use correct SPN format for VZW WFC.

Bug: 30474919
Change-Id: I0f0dbda86fb441d2b8c10a2934650b9ecec63e19
diff --git a/assets/carrier_config_311480.xml b/assets/carrier_config_311480.xml
index 2579644..1694aa8 100644
--- a/assets/carrier_config_311480.xml
+++ b/assets/carrier_config_311480.xml
@@ -54,5 +54,6 @@
         <boolean name="disable_severe_when_extreme_disabled_bool" value="false" />
         <boolean name="mmsCloseConnection" value="true"/>
         <boolean name="notify_vt_handover_to_wifi_failure_bool" value="true" />
+        <int name="wfc_spn_format_idx_int" value="1" />
     </carrier_config>
 </carrier_config_list>