Bump tensorflow-gpu from 1.15.4 to 2.12.0 in /tf

Bumps [tensorflow-gpu](https://github.com/tensorflow/tensorflow) from 1.15.4 to 2.12.0.
- [Release notes](https://github.com/tensorflow/tensorflow/releases)
- [Changelog](https://github.com/tensorflow/tensorflow/blob/master/RELEASE.md)
- [Commits](https://github.com/tensorflow/tensorflow/compare/v1.15.4...v2.12.0)

---
updated-dependencies:
- dependency-name: tensorflow-gpu
  dependency-type: direct:production
...

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tf/requirements-gpu.txt

@@ -4,7 +4,7 @@ numpy==1.16.4
 pandas==0.23.4
 scikit-learn==0.19.2
 scipy==1.1.0
-tensorflow-gpu==1.15.4
+tensorflow-gpu==2.12.0
 requests
 bokeh==2.1.1
 onnx==1.8.0