Bump tensorflow-gpu from 2.4.0 to 2.5.1

Bumps [tensorflow-gpu](https://github.com/tensorflow/tensorflow) from 2.4.0 to 2.5.1.
- [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/v2.4.0...v2.5.1)

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

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requirements.txt

@@ -22,7 +22,7 @@ scipy==1.6.3
 six==1.12.0
 tensorboard==2.0.0
 tensorflow-estimator==2.0.0
-tensorflow-gpu==2.4.0
+tensorflow-gpu==2.5.1
 termcolor==1.1.0
 Werkzeug==0.16.0
 wrapt==1.11.2