Bump tensorflow from 1.12.0 to 1.15.2 in /dm_intent

Bumps [tensorflow](https://github.com/tensorflow/tensorflow) from 1.12.0 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@v1.12.0...v1.15.2)

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

Author: dependabot[bot]

dm_intent/requirements.txt

@@ -152,7 +152,7 @@ smach-ros==2.0.1
 smart-open==2.1.0
 smclib==1.8.5
 tensorboard==1.12.2
-tensorflow==1.12.0
+tensorflow==1.15.2
 termcolor==1.1.0
 tf==1.12.1
 tf-conversions==1.12.1