chore(deps): update pillow requirement from ~=6.0.0 to ~=6.1.0 (#6139)

Updates the requirements on [pillow](https://github.com/python-pillow/Pillow) to permit the latest version.
- [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...6.1.0)

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

requirements/common.txt

@@ -19,7 +19,7 @@ humanize~=0.5.1
 celery~=4.3
 redis~=3.2
 apscheduler~=3.6.0
-pillow~=6.0.0
+pillow~=6.1.0
 amqp~=2.5
 gunicorn~=19.9
 boto~=2.49