Bump tensorflow from 1.14.0 to 1.15.0

Bumps [tensorflow](https://github.com/tensorflow/tensorflow) from 1.14.0 to 1.15.0.
- [Release notes](https://github.com/tensorflow/tensorflow/releases)
- [Changelog](https://github.com/tensorflow/tensorflow/blob/master/RELEASE.md)
- [Commits](tensorflow/tensorflow@v1.14.0...v1.15.0)

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

Author: dependabot[bot]

requirements-docker.txt

@@ -3,5 +3,5 @@ scikit-image==0.15.0
 seaborn==0.9.0
 sklearn==0.0
 scikit-learn==0.21.3
-tensorflow==1.14.0
+tensorflow==1.15.0
 joblib==0.14.0