Bump pillow from 7.1.1 to 8.1.1

Bumps [pillow](https://github.com/python-pillow/Pillow) from 7.1.1 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@7.1.1...8.1.1)

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

Author: dependabot[bot]

requirements.txt

@@ -12,7 +12,7 @@ numpy==1.18.2
 openpyxl==3.0.3
 pandas==1.0.3
 pandas-bokeh==0.4.2
-pillow==7.1.1
+pillow==8.1.1
 psutil==5.7.0
 pur==5.3.0
 rise==5.6.1