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](https://github.com/python-pillow/Pillow/compare/5.4.1...6.2.0

)

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

requirements.txt

@@ -33,7 +33,7 @@ gunicorn==20.0.4
 mailchimp3==3.0.12
 mistune==0.8.4
 more-itertools==7.2.0
-Pillow==5.4.1
+Pillow==6.2.0
 psycopg2==2.7.3.1
 reportlab==3.5.34
 social_auth_app_django==3.1.0