Update pillow requirement from ~=9.0.1 to ~=9.1.0 in /generator

Updates the requirements on [pillow](https://github.com/python-pillow/Pillow) to permit the latest version.
- [Release notes](https://github.com/python-pillow/Pillow/releases)
- [Changelog](https://github.com/python-pillow/Pillow/blob/main/CHANGES.rst)
- [Commits](python-pillow/Pillow@9.0.1...9.1.0)

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

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

generator/requirements.txt

@@ -1,3 +1,3 @@
-Pillow~=9.0.1
+Pillow~=9.1.0
 requests~=2.27.1
 libscrc~=1.7.1