Bump pillow from 8.0.1 to 8.1.0

Bumps [pillow](https://github.com/python-pillow/Pillow) from 8.0.1 to 8.1.0.
- [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/8.0.1...8.1.0)

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

requirements.txt

@@ -7,7 +7,7 @@ django-extensions>=2.2,<3.2
 psycopg2-binary>=2.8,<2.9
 
 # Sandbox
-Pillow==8.0.1
+Pillow==8.1.0
 Whoosh==2.7.4
 django-environ==0.4.5
 django-redis==4.12.1