Enable unused-private-field warning (#13450)

Summary:
Pull Request resolved: #13450

Pull Request resolved: facebook/react-native#22065

This diff enables -Wunused-private-field clang warning for Android builds and fixes all broken targets.

Reviewed By: gkmhub

Differential Revision: D12881793

fbshipit-source-id: 515555661e137be9e7b20eac9b5bdcb549d6a094

Author: Uladzislau Paulovich

caffe2/core/nomnigraph/include/nomnigraph/Representations/NeuralNet.h

@@ -153,7 +153,6 @@ class CAFFE2_API NeuralNetData : public Data {
 
  private:
   NNDataKind kind_;
-  size_t version_ = 0;
 };
 
 class CAFFE2_API Tensor : public NeuralNetData {