Bump transformers in /review-sentiment/sentiment-backend

Bumps [transformers](https://github.com/huggingface/transformers) from 4.21.3 to 4.28.1.
- [Release notes](https://github.com/huggingface/transformers/releases)
- [Commits](huggingface/transformers@v4.21.3...v4.28.1)

---
updated-dependencies:
- dependency-name: transformers
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

review-sentiment/sentiment-backend/requirements-base.txt

@@ -4,7 +4,7 @@ numpy
 pydantic==1.10.2
 fastapi==0.82.0
 uvicorn==0.18.3
-transformers==4.21.3
+transformers==4.28.1
 captum==0.5.0
 
 git+https://github.com/xai-demonstrator/xai-demonstrator.git@6f230206fd06fc0b43fc1d430a4ad804d2605123#egg=xaidemo&subdirectory=common/backend-utils