Bump pillow from 5.1.0 to 8.3.2

Bumps [pillow](https://github.com/python-pillow/Pillow) from 5.1.0 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](python-pillow/Pillow@5.1.0...8.3.2)

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

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

Author: dependabot[bot]

manager/requirements.txt

@@ -17,7 +17,7 @@ Jinja2==2.10
 kombu==4.2.0
 MarkupSafe==1.0
 numpy==1.14.3
-Pillow==5.1.0
+Pillow==8.3.2
 pommerman==0.2.0
 pyglet==1.4.0a1
 pytz==2018.4

requirements.txt

@@ -1,7 +1,7 @@
 docker~=3.1
 gym~=0.10.5
 scipy~=1.0
-Pillow~=5.0
+Pillow~=8.3
 ruamel.yaml~=0.15
 Flask~=0.12
 requests~=2.18