Bump tensorflow-gpu from 1.13.1 to 2.4.0

Bumps [tensorflow-gpu](https://github.com/tensorflow/tensorflow) from 1.13.1 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@v1.13.1...v2.4.0)

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

Author: dependabot[bot]

requirements.txt

@@ -6,7 +6,7 @@ mlflow==1.2.0
 xgboost==0.90
 lightgbm==2.3.0
 gensim==3.8.1
-tensorflow-gpu==1.13.1
+tensorflow-gpu==2.4.0
 Keras==2.2.5
 rank-bm25==0.2.1
 Distance==0.1.3