build(deps): bump elasticsearch from 8.17.1 to 9.0.1 in /backend

Bumps [elasticsearch](https://github.com/elastic/elasticsearch-py) from 8.17.1 to 9.0.1.
- [Release notes](https://github.com/elastic/elasticsearch-py/releases)
- [Commits](https://github.com/elastic/elasticsearch-py/compare/v8.17.1...v9.0.1)

---
updated-dependencies:
- dependency-name: elasticsearch
  dependency-version: 9.0.1
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

backend/requirements.txt

@@ -49,7 +49,7 @@ pymilvus==2.5.0
 qdrant-client~=1.12.0
 opensearch-py==2.8.0
 playwright==1.49.1 # Caution: version must match docker-compose.playwright.yaml
-elasticsearch==8.17.1
+elasticsearch==9.0.1
 pinecone==6.0.2
 
 transformers