CtsAndroidTestBase27ApiSignatureTestCases to CtsAndroidTestBase28ApiSignatureTestCases
from TEST MAPPING file.
Reason: CtsAndroidTestBase27ApiSignatureTestCases has been renamed to
CtsAndroidTestBase28ApiSignatureTestCases, so correct this.
Bug: 129464829
Test: unittests.
Change-Id: I7e0184746c81f9564e67074c5d34d98fc2380317