Bump tensorflow

Bumps [tensorflow](https://github.com/tensorflow/tensorflow) from 1.0.0 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@v1.0.0...v1.15.4)

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Author: dependabot[bot]

Jupyter notebooks/deep-learning-master/intro-to-tflearn/requirements.txt

@@ -42,7 +42,7 @@ qtconsole==4.3.0
 scipy==0.19.0
 simplegeneric==0.8.1
 six==1.10.0
-tensorflow==1.0.0
+tensorflow==1.15.4
 terminado==0.6
 testpath==0.3
 tflearn==0.3