Bump pillow from 5.4.1 to 7.1.0 in /docs/samples/explanation/aix/mnist (

kubeflow#1190)

Bumps [pillow](https://github.com/python-pillow/Pillow) from 5.4.1 to 7.1.0.
- [Release notes](https://github.com/python-pillow/Pillow/releases)
- [Changelog](https://github.com/python-pillow/Pillow/blob/master/CHANGES.rst)
- [Commits](python-pillow/Pillow@5.4.1...7.1.0)

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

docs/samples/explanation/aix/mnist/requirements.txt

@@ -60,7 +60,7 @@ pandocfilters==1.4.2
 parso==0.6.2
 pexpect==4.8.0
 pickleshare==0.7.5
-Pillow==5.4.1
+Pillow==7.1.0
 prometheus-client==0.7.1
 prompt-toolkit==3.0.5
 protobuf==3.11.3