Bump pillow from 7.2.0 to 8.1.1

Bumps [pillow](https://github.com/python-pillow/Pillow) from 7.2.0 to 8.1.1.
- [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/7.2.0...8.1.1)

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

requirements.txt

@@ -47,7 +47,7 @@ owotext==1.0.2
 packaging==20.4
 Paginator==0.5.1
 pbr==5.4.5
-Pillow==7.2.0
+Pillow==8.1.1
 protobuf==3.12.2
 psutil==5.7.2
 pycodestyle==2.6.0