Add TEST_MAPPING for CtsSystemApiSignatureTestCases

Bug: 124209375
Test: m and watch if treehugger triggers the test
Change-Id: I2c4320ffc5ac30b9b6ac4991570dee9415bb2ca0
diff --git a/api/TEST_MAPPING b/api/TEST_MAPPING
index 2cdf54b..4d22d0b 100644
--- a/api/TEST_MAPPING
+++ b/api/TEST_MAPPING
@@ -4,6 +4,9 @@
       "name": "CtsCurrentApiSignatureTestCases"
     },
     {
+      "name": "CtsSystemApiSignatureTestCases"
+    },
+    {
       "name": "GtsUnofficialApisUsageTestCases"
     }
   ]