Bump pillow from 5.1.0 to 9.0.0

Bumps [pillow](https://github.com/python-pillow/Pillow) from 5.1.0 to 9.0.0.
- [Release notes](https://github.com/python-pillow/Pillow/releases)
- [Changelog](https://github.com/python-pillow/Pillow/blob/main/CHANGES.rst)
- [Commits](https://github.com/python-pillow/Pillow/compare/5.1.0...9.0.0)

---
updated-dependencies:
- dependency-name: pillow
  dependency-type: direct:production
...

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

requirements.txt

@@ -5,7 +5,7 @@ async-timeout==2.0.1
 attrs==17.4.0
 Django==2.0.4
 multidict==4.1.0
-Pillow==5.1.0
+Pillow==9.0.0
 psycopg2-binary==2.7.4
 pytz==2018.3
 sentry-sdk==0.20.3