Bump tf2onnx from 1.14.0 to 1.15.1

Bumps [tf2onnx](https://github.com/onnx/tensorflow-onnx) from 1.14.0 to 1.15.1.
- [Release notes](https://github.com/onnx/tensorflow-onnx/releases)
- [Commits](onnx/tensorflow-onnx@v1.14.0...v1.15.1)

---
updated-dependencies:
- dependency-name: tf2onnx
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

requirements.txt

@@ -9,7 +9,7 @@ rembg==2.0.50
 onnxruntime==1.15.1
 scipy==1.11.2
 # Export to onnx
-tf2onnx==1.14.0 # Not upgradable due to incompatibility with onnxruntime/tf
+tf2onnx==1.15.1 # Not upgradable due to incompatibility with onnxruntime/tf
 # Explaining the model
 shap==0.42.1
 scikit-learn==1.3.0