Bump pillow from 6.2.2 to 8.1.1

Bumps [pillow](https://github.com/python-pillow/Pillow) from 6.2.2 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@6.2.2...8.1.1)

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

requirements.txt

@@ -6,4 +6,4 @@ ffmpeg-python==0.1.17
 youtube-dl>=2019.4.17
 jupyterlab
 opencv-python>=3.3.0.10
-pillow==6.2.2
+pillow==8.1.1