Bump pillow from 7.0.0 to 8.3.2

Bumps [pillow](https://github.com/python-pillow/Pillow) from 7.0.0 to 8.3.2.
- [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/7.0.0...8.3.2)

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

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

requirements.txt

@@ -21,7 +21,7 @@ mock==4.0.1
 networkx==2.4
 nibabel==3.0.1
 numpy==1.18.1
-Pillow==7.0.0
+Pillow==8.3.2
 protobuf==3.11.3
 pyparsing==2.4.6
 PySocks==1.7.1