Skipping test on GSI + first_api_level < U

The test is marked as assumption failed for
Key attestation fails on the combination of the build with the vendor
froze on the Android T base build and Android U/V GSI build because
the attestation properties ro.product.*_for_attestation have to be
present in vendor properties files.

Bug: 308122994
Test: atest
CtsKeystoreTestCases: android.keystore.cts.KeyAttestationTest

Change-Id: I35f4a5c7ee10c37cde3d406d46bff81fce2a72f0