Add RTT config for select USA carriers

Enable RTT for certain USA carriers

Bug: 72665193
Test: manual
Change-Id: Ib9a5eb6a05401a6ee5399018d7843a11a10016c7
diff --git a/assets/carrier_config_310300.xml b/assets/carrier_config_310300.xml
index a2a71a1..8e1cc54 100644
--- a/assets/carrier_config_310300.xml
+++ b/assets/carrier_config_310300.xml
@@ -1,6 +1,7 @@
 <?xml version='1.0' encoding='utf-8' standalone='yes' ?>
 <carrier_config_list>
     <carrier_config>
+        <boolean name="rtt_supported_bool" value="true" />
         <boolean name="carrier_volte_available_bool" value="true" />
         <boolean name="carrier_volte_tty_supported_bool" value="false" />
         <boolean name="carrier_wfc_ims_available_bool" value="true" />