Bump pillow from 5.4.1 to 6.2.0

Bumps [pillow](https://github.com/python-pillow/Pillow) from 5.4.1 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@5.4.1...6.2.0)

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

Author: dependabot[bot]

requirements.txt

@@ -66,7 +66,7 @@ pandocfilters==1.4.2
 parso==0.3.1
 patsy==0.5.1
 pickleshare==0.7.5
-Pillow==5.4.1
+Pillow==6.2.0
 prometheus-client==0.5.0
 prompt-toolkit==2.0.7
 protobuf==3.6.1