Prepare CtsTetheringTestLatestSdk for presubmit by adding it to postsubmit

This commit adds CtsTetheringTestLatestSdk to the postsubmit
configuration. This is a preparatory step towards moving the test to
presubmit, ensuring it runs regularly and catches issues earlier in the
development cycle.

Test: TH
Change-Id: I6932b0b660a675a20102d2683119f689557d8590
diff --git a/TEST_MAPPING b/TEST_MAPPING
index 1d2041b..d91136a 100644
--- a/TEST_MAPPING
+++ b/TEST_MAPPING
@@ -257,6 +257,9 @@
     // TODO: Move to presumit after meet SLO requirement.
     {
       "name": "NetworkStaticLibHostPythonTests"
+    },
+    {
+      "name": "CtsTetheringTestLatestSdk"
     }
   ],
   "mainline-presubmit": [