[Thread] add Thread tests to mts-tethering

Bug: 322142548
Change-Id: I71af1787b23be4c27d26b30498408631c2955012
diff --git a/thread/tests/unit/Android.bp b/thread/tests/unit/Android.bp
index 291475e..f59500e 100644
--- a/thread/tests/unit/Android.bp
+++ b/thread/tests/unit/Android.bp
@@ -29,6 +29,7 @@
     ],
     test_suites: [
         "general-tests",
+        "mts-tethering",
     ],
     static_libs: [
         "frameworks-base-testutils",