Bump tensorflow-gpu from 1.15.2 to 2.4.0 in /commons

Bumps [tensorflow-gpu](https://github.com/tensorflow/tensorflow) from 1.15.2 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@v1.15.2...v2.4.0)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

commons/requirements.19.06.txt

@@ -236,7 +236,7 @@ termcolor==1.1.0
 terminado==0.8.3
 test-generator==0.1.1
 testpath==0.4.4
-tensorflow-gpu==1.13.2
+tensorflow-gpu==2.4.0
 tf2onnx==1.5.5
 toml==0.10.0
 toolz==0.10.0

commons/requirements.19.09.txt

@@ -236,7 +236,7 @@ termcolor==1.1.0
 terminado==0.8.3
 test-generator==0.1.1
 testpath==0.4.4
-tensorflow-gpu==1.14
+tensorflow-gpu==2.4.0
 tf2onnx==1.5.5
 toml==0.10.0
 toolz==0.10.0

commons/requirements.20.03.cuda10.txt

@@ -236,7 +236,7 @@ termcolor==1.1.0
 terminado==0.8.3
 test-generator==0.1.1
 testpath==0.4.4
-tensorflow-gpu==1.15.2
+tensorflow-gpu==2.4.0
 tf2onnx==1.5.5
 toml==0.10.0
 toolz==0.10.0