Update VtsHalRadioTargetTest: null cipher disablement APIs are optional

Mark isNullCipherAndIntegrityEnabled and setNullCipherAndIntegrityEnabled as optional.

Bug: b/307361090
Test: m & atest VtsHalRadioTargetTest
Change-Id: I74a05b068d415cefbd87cdc53e3cc099529ad04a
1 file changed