Bump pillow from 6.2.0 to 6.2.1

Bumps [pillow](https://github.com/python-pillow/Pillow) from 6.2.0 to 6.2.1.
- [Release notes](https://github.com/python-pillow/Pillow/releases)
- [Changelog](https://github.com/python-pillow/Pillow/blob/master/CHANGES.rst)
- [Commits](python-pillow/Pillow@6.2.0...6.2.1)

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

requirements.txt

@@ -3,7 +3,7 @@ lmdb==0.97
 matplotlib==3.1.1
 numpy==1.16.2
 opencv-python==4.1.0.25
-Pillow==6.2.0
+Pillow==6.2.1
 scikit-image==0.15.0
 scikit-learn==0.21.3
 scipy==1.3.1