Bump tensorflow (#1574)

Bumps [tensorflow](https://github.com/tensorflow/tensorflow) from 1.13.1 to 1.15.4.
- [Release notes](https://github.com/tensorflow/tensorflow/releases)
- [Changelog](https://github.com/tensorflow/tensorflow/blob/master/RELEASE.md)
- [Commits](tensorflow/tensorflow@v1.13.1...v1.15.4)

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

sagemaker_batch_transform/tensorflow_open-images_tfrecord/code/requirements.txt

@@ -1 +1 @@
-tensorflow==1.13.1
+tensorflow==1.15.4