Bump pillow from 3.3.1 to 8.3.2 in /sticker

Bumps [pillow](https://github.com/python-pillow/Pillow) from 3.3.1 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](https://github.com/python-pillow/Pillow/compare/3.3.1...8.3.2)

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

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

sticker/requirements.txt

@@ -1,5 +1,5 @@
 lxml == 3.5.0
 requests == 2.9.1
 urllib3 == 1.13.1
-Pillow == 3.3.1
+Pillow == 8.3.2
 beautifulsoup4 == 4.5.1