Bump tensorflow from 2.3.0 to 2.3.1 in /noise-contrastive-priors

Bumps [tensorflow](https://github.com/tensorflow/tensorflow) from 2.3.0 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@v2.3.0...v2.3.1)

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

noise-contrastive-priors/requirements.txt

@@ -1,4 +1,4 @@
 scipy==1.4.1
-tensorflow==2.3.0
+tensorflow==2.3.1
 tensorflow-probability==0.11.0
 seaborn==0.11.0