Update pillow requirement from <9.0.0,>=8.4.0 to >=8.4.0,<10.0.0

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@8.4.0...9.0.0)

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

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

requirements.txt

@@ -1,5 +1,5 @@
 numpy >=1.18.4,<1.22.2
-Pillow >=8.4.0,<9.0.0
+Pillow >=8.4.0,<10.0.0
 scikit-image >=0.19.0,<0.19.2
 scipy >=1.5.0,<1.7.4
 openslide-python