Update TEST_MAPPING

Test: None

Bug: 236006683
Change-Id: I23fcb0a4866b26a8b2fa60a50fd30ac7ca98bbf3
diff --git a/TEST_MAPPING b/TEST_MAPPING
index e6612ed..209b12d 100644
--- a/TEST_MAPPING
+++ b/TEST_MAPPING
@@ -14,11 +14,6 @@
       "path": "external/rust/crates/unicode-xid"
     }
   ],
-  "postsubmit": [
-    {
-      "name": "cast_test_src_lib"
-    }
-  ],
   "presubmit": [
     {
       "name": "cast_test_src_lib"