Add test for TREL service not unpublish when feature disabled

Bug: 379804913

Change-Id: I8dd98a0605dd7e9c53b144f6227791a2080e8263
diff --git a/thread/TEST_MAPPING b/thread/TEST_MAPPING
index 34d67bb..40842f1 100644
--- a/thread/TEST_MAPPING
+++ b/thread/TEST_MAPPING
@@ -13,6 +13,9 @@
   "postsubmit": [
     {
       "name": "ThreadNetworkMultiDeviceTests"
+    },
+    {
+      "name": "ThreadNetworkTrelDisabledTests"
     }
   ]
 }