Relax TestGpuNnapi accuracy check with a tolerance. am: 97b7166ad0 am: a2cd69d871

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/modules/NeuralNetworks/+/15756398

Change-Id: Id34ab7ac0c0ac1944420917571db049090c2ed88