Rename CtsAndroidTestBase29ApiSignatureTestCases in TEST MAPPING file.

Reason: CtsAndroidTestBase28ApiSignatureTestCases has been renamed to
CtsAndroidTestBase29ApiSignatureTestCases, so correct this.

Bug: 233937435

Test: unittest
Change-Id: I3b1be4ce4033104fcb86027fe596c852d64e6fa1

test-base/api/TEST_MAPPING

 {
   "presubmit": [
     {
-      "name": "CtsAndroidTestBase28ApiSignatureTestCases"
+      "name": "CtsAndroidTestBase29ApiSignatureTestCases"
     }
   ]
 }