Bump tensorflow-gpu from 1.1.0 to 1.15.2

Bumps [tensorflow-gpu](https://github.com/tensorflow/tensorflow) from 1.1.0 to 1.15.2.
- [Release notes](https://github.com/tensorflow/tensorflow/releases)
- [Changelog](https://github.com/tensorflow/tensorflow/blob/master/RELEASE.md)
- [Commits](tensorflow/tensorflow@v1.1.0...v1.15.2)

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

Author: dependabot[bot]

requirements.txt

@@ -102,7 +102,7 @@ six==1.11.0
 sparkmagic==0.12.5
 tensorboard==1.7.0
 tensorflow==1.7.1
-tensorflow-gpu==1.1.0
+tensorflow-gpu==1.15.2
 termcolor==1.1.0
 terminado==0.8.1
 testpath==0.3.1