Bump pillow from 2.8.1 to 9.3.0

Bumps [pillow](https://github.com/python-pillow/Pillow) from 2.8.1 to 9.3.0.
- [Release notes](https://github.com/python-pillow/Pillow/releases)
- [Changelog](https://github.com/python-pillow/Pillow/blob/main/CHANGES.rst)
- [Commits](python-pillow/Pillow@2.8.1...9.3.0)

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

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

requirements.txt

@@ -4,7 +4,7 @@ Flask-Cors==2.0.1
 Flask-Mail==0.9.1
 Jinja2==2.11.3
 MarkupSafe==0.23
-Pillow==2.8.1
+Pillow==9.3.0
 PyYAML==3.11
 Werkzeug==0.15.3
 argparse==1.2.1