build(deps): bump chromadb from 0.6.2 to 0.6.3 in /backend

Bumps [chromadb](https://github.com/chroma-core/chroma) from 0.6.2 to 0.6.3.
- [Release notes](https://github.com/chroma-core/chroma/releases)
- [Changelog](https://github.com/chroma-core/chroma/blob/main/RELEASE_PROCESS.md)
- [Commits](https://github.com/chroma-core/chroma/compare/0.6.2...0.6.3)

---
updated-dependencies:
- dependency-name: chromadb
  dependency-version: 0.6.3
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

backend/requirements.txt

@@ -44,7 +44,7 @@ langchain==0.3.19
 langchain-community==0.3.18
 
 fake-useragent==2.1.0
-chromadb==0.6.2
+chromadb==0.6.3
 pymilvus==2.5.0
 qdrant-client~=1.12.0
 opensearch-py==2.8.0