Bump pillow from 6.2.0 to 8.1.1

Bumps [pillow](https://github.com/python-pillow/Pillow) from 6.2.0 to 8.1.1.
- [Release notes](https://github.com/python-pillow/Pillow/releases)
- [Changelog](https://github.com/python-pillow/Pillow/blob/master/CHANGES.rst)
- [Commits](python-pillow/Pillow@6.2.0...8.1.1)

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

requirements.txt

@@ -63,7 +63,7 @@ nose==1.3.7
 oauthlib==3.0.1
 openapi-codec==1.3.2
 pathlib==1.0.1
-Pillow==6.2.0
+Pillow==8.1.1
 psycopg2==2.7.7
 pusher==2.1.3
 py-vapid==1.5.0