Bump tensorflow-gpu from 1.13.1 to 1.15.2 in /OneStage/yolo

Bumps [tensorflow-gpu](https://github.com/tensorflow-gpu/tensorflow-gpu) from 1.13.1 to 1.15.2.
- [Release notes](https://github.com/tensorflow-gpu/tensorflow-gpu/releases)
- [Commits](https://github.com/tensorflow-gpu/tensorflow-gpu/commits)

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

Author: dependabot[bot]

OneStage/yolo/requirements.txt

@@ -1,5 +1,5 @@
 Keras==2.3.1
-tensorflow-gpu==1.13.1
+tensorflow-gpu==1.15.2
 numpy==1.15.0
 opencv-python==4.2.0
 scikit-learn==0.21.2