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>

requirements.txt

@@ -1,5 +1,5 @@
 Jinja2==2.11.3
 markdown2==2.4.0
 selenium==3.14.1
-Pillow==8.1.1
+Pillow==8.3.2
 Pygments==2.7.4