Bump pillow from 4.2.1 to 9.0.0

Bumps [pillow](https://github.com/python-pillow/Pillow) from 4.2.1 to 9.0.0.
- [Release notes](https://github.com/python-pillow/Pillow/releases)
- [Changelog](https://github.com/python-pillow/Pillow/blob/main/CHANGES.rst)
- [Commits](python-pillow/Pillow@4.2.1...9.0.0)

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

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

requirements.txt

@@ -44,7 +44,7 @@ pathlib2==2.3.0
 pbr==3.1.1
 pexpect==4.2.1
 pickleshare==0.7.4
-Pillow==4.2.1
+Pillow==9.0.0
 prompt-toolkit==1.0.14
 protobuf==3.3.0
 ptyprocess==0.5.2