Bump pillow from 8.1.1 to 8.3.2

Bumps [pillow](https://github.com/python-pillow/Pillow) from 8.1.1 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](python-pillow/Pillow@8.1.1...8.3.2)

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

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

Author: dependabot[bot]

requirements.txt

@@ -9,7 +9,7 @@ matplotlib==3.1.1
 networkx==2.4     
 numpy==1.17.4  
 opencv-contrib-python==4.1.1.26
-Pillow==8.1.1   
+Pillow==8.3.2   
 pip==19.3.1  
 pyparsing==2.4.5   
 python-dateutil==2.8.1