mediapc: Remove redundant secureWithUnsecure check

MultiDecoderPairPerfTest was trying to invoke more than the
supported number of instances in some cases because
secureWithUnsecure combination ignored the number of instances supported.

Test: atest android.mediapc.cts.MultiDecoderPairPerfTest
Bug: 322899169

Change-Id: I85b7f9a413f02fa2ecb70a96c33de4bd937d58ca
1 file changed