Build(deps): Bump pypdf from 6.6.2 to 6.7.1 in /backend in the uv group across 1 directory (#221)

Build(deps): Bump pypdf in /backend in the uv group across 1 directory

Bumps the uv group with 1 update in the /backend directory: [pypdf](https://github.com/py-pdf/pypdf).


Updates `pypdf` from 6.6.2 to 6.7.1
- [Release notes](https://github.com/py-pdf/pypdf/releases)
- [Changelog](https://github.com/py-pdf/pypdf/blob/main/CHANGELOG.md)
- [Commits](py-pdf/pypdf@6.6.2...6.7.1)

---
updated-dependencies:
- dependency-name: pypdf
  dependency-version: 6.7.1
  dependency-type: direct:production
  dependency-group: uv
...

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Author: dependabot[bot]

backend/pyproject.toml

@@ -30,7 +30,7 @@ dependencies = [
     "protobuf>=5.29.6",
     "psycopg2-binary>=2.9.11",
     "pydantic>=2.11.7",
-    "pypdf==6.6.2",
+    "pypdf==6.7.1",
     "rank-bm25==0.2.2",
     "rich>=13.7.0",
     "sentence-transformers>=5.1.0",