TestGpuNnapi: add missing sType for VkExternalBufferProperties am: ff83e506bf

Original change: https://android-review.googlesource.com/c/platform/packages/modules/NeuralNetworks/+/2308100

Change-Id: I3ce47a764684ee1a4568df17c75185df060b77a0
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>