Bump onnx from 1.15.0 to 1.16.0 in /src/bindings/python

Bumps [onnx](https://github.com/onnx/onnx) from 1.15.0 to 1.16.0.
- [Release notes](https://github.com/onnx/onnx/releases)
- [Changelog](https://github.com/onnx/onnx/blob/main/docs/Changelog-ml.md)
- [Commits](onnx/onnx@v1.15.0...v1.16.0)

---
updated-dependencies:
- dependency-name: onnx
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

src/bindings/python/constraints.txt

@@ -21,4 +21,4 @@ paddlepaddle==2.5.2
 tensorflow>=1.15.5,<2.16.0
 six~=1.16.0
 protobuf>=3.18.1,<4.0.0
-onnx==1.15.0
+onnx==1.16.0