Bump pillow from 8.2.0 to 8.3.2 in /tests/python/unit

Bumps [pillow](https://github.com/python-pillow/Pillow) from 8.2.0 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@8.2.0...8.3.2)

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

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

Author: dependabot[bot]

tests/python/unit/requirements.txt

@@ -1,4 +1,4 @@
 pandas>=1.0,<1.1
 pytest==6.2.1
 allure-pytest==2.8.29
-Pillow==8.2.0
+Pillow==8.3.2