Bump tensorflow in /components/outlier-detection/vae

Bumps [tensorflow](https://github.com/tensorflow/tensorflow) from 1.13.1 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@v1.13.1...v1.15.0)

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

components/outlier-detection/vae/requirements.txt

@@ -1,5 +1,5 @@
 keras==2.2.2
-tensorflow==1.13.1
+tensorflow==1.15.0
 numpy==1.14.5
 argparse==1.1
 pandas==0.23.4