Bump tensorflow from 2.1.0 to 2.4.0 in /prediction-experiments/python-nb

Bumps [tensorflow](https://github.com/tensorflow/tensorflow) from 2.1.0 to 2.4.0.
- [Release notes](https://github.com/tensorflow/tensorflow/releases)
- [Changelog](https://github.com/tensorflow/tensorflow/blob/master/RELEASE.md)
- [Commits](tensorflow/tensorflow@v2.1.0...v2.4.0)

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

Author: dependabot[bot]

prediction-experiments/python-nb/requirements.txt

@@ -8,5 +8,5 @@ pandas==1.0.1
 Keras==2.3.1              
 Keras-Applications==1.0.8              
 Keras-Preprocessing==1.1.0   
-tensorflow==2.1.0              
+tensorflow==2.4.0              
 tensorflow-estimator==2.1.0