Bump pillow from 7.1.2 to 8.1.1

Bumps [pillow](https://github.com/python-pillow/Pillow) from 7.1.2 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](python-pillow/Pillow@7.1.2...8.1.1)

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

Author: dependabot[bot]

requirements.txt

@@ -28,7 +28,7 @@ oauthlib==3.1.0
 openpyxl==3.0.3
 orderedmultidict==1.0.1
 pdfminer.six==20200402
-Pillow==7.1.2
+Pillow==8.1.1
 psutil==5.7.0
 pycparser==2.20
 pycryptodome==3.9.7