Bump pillow from 2.3.0 to 8.1.1 in /ODSA-django

Bumps [pillow](https://github.com/python-pillow/Pillow) from 2.3.0 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@2.3.0...8.1.1)

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

Author: dependabot[bot]

ODSA-django/requirements.txt

@@ -3,7 +3,7 @@ Django==1.4.3
 #Landscape-Client==14.12
 MySQL-python==1.2.3
 #PAM==0.4.2
-Pillow==2.3.0
+Pillow==8.1.1
 PyYAML==3.10
 SecretStorage==2.0.0
 Twisted==13.1.0