Add back tethering to mainline-postsubmit

Tethering was removed from mainline-postsubmit while Connectivity was
being added to it, but it can run in postsubmit again now.

If the runs are successful, it can be added to presubmit as well.

Ignore-AOSP-First: Partial revert of change that did not go to AOSP
Bug: 177290955
Test: TH needs to test postsubmit

Change-Id: I5d5dbccd8d14be573104947412a76578b2d7a6c1
diff --git a/TEST_MAPPING b/TEST_MAPPING
index d7d4bcb..030a4c7 100644
--- a/TEST_MAPPING
+++ b/TEST_MAPPING
@@ -27,8 +27,7 @@
   // Tests on physical devices with SIM cards: postsubmit only for capacity constraints
   "mainline-postsubmit": [
     {
-      // TODO: add back the tethering module when updatable in this branch
-      "name": "CtsNetTestCasesLatestSdk[CaptivePortalLoginGoogle.apk+NetworkStackGoogle.apk+com.google.android.resolv.apex]",
+      "name": "CtsNetTestCasesLatestSdk[CaptivePortalLoginGoogle.apk+NetworkStackGoogle.apk+com.google.android.resolv.apex+com.google.android.tethering.apex]",
       "keywords": ["sim"]
     }
   ],