Bump pillow in /examples/v1beta1/trial-images/pytorch-mnist

Bumps [pillow](https://github.com/python-pillow/Pillow) from 6.2.2 to 9.0.1.
- [Release notes](https://github.com/python-pillow/Pillow/releases)
- [Changelog](https://github.com/python-pillow/Pillow/blob/main/CHANGES.rst)
- [Commits](python-pillow/Pillow@6.2.2...9.0.1)

---
updated-dependencies:
- dependency-name: pillow
  dependency-type: direct:production
...

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

examples/v1beta1/trial-images/pytorch-mnist/requirements.txt

@@ -1,4 +1,4 @@
 cloudml-hypertune==0.1.0.dev6
 torch==1.0.0
 torchvision==0.2.1
-Pillow==6.2.2
+Pillow==9.0.1