Bump tensorflow-gpu from 2.2.0 to 2.3.1 in /batch_processing

Bumps [tensorflow-gpu](https://github.com/tensorflow/tensorflow) from 2.2.0 to 2.3.1.
- [Release notes](https://github.com/tensorflow/tensorflow/releases)
- [Changelog](https://github.com/tensorflow/tensorflow/blob/master/RELEASE.md)
- [Commits](tensorflow/tensorflow@v2.2.0...v2.3.1)

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Author: dependabot[bot]

batch_processing/requirements.txt

@@ -49,7 +49,7 @@ soundfile==0.10.3.post1
 tensorboard==2.1.1
 tensorboard-plugin-wit==1.6.0.post3
 tensorflow-estimator==2.1.0
-tensorflow-gpu==2.2.0
+tensorflow-gpu==2.3.1
 tensorflow-gpu-estimator==2.2.0
 termcolor==1.1.0
 toml==0.10.1