Bump pillow from 6.0.0 to 6.2.0

Bumps [pillow](https://github.com/python-pillow/Pillow) from 6.0.0 to 6.2.0.
- [Release notes](https://github.com/python-pillow/Pillow/releases)
- [Changelog](https://github.com/python-pillow/Pillow/blob/master/CHANGES.rst)
- [Commits](python-pillow/Pillow@6.0.0...6.2.0)

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

requirements.txt

@@ -3,7 +3,7 @@ chardet==3.0.4
 idna==2.8
 joblib==0.13.2
 numpy==1.16.4
-Pillow==6.0.0
+Pillow==6.2.0
 pyzmq==18.0.1
 requests==2.22.0
 scipy==1.3.0