Relax TestGpuNnapi accuracy check with a tolerance. am: 97b7166ad0 am: a2cd69d871 am: 627387d9e8

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

Change-Id: I92001b7a8a4aeafb8470d10247464c940d8d592b