chore: bump pypdf from 6.7.5 to 6.9.1

Bumps [pypdf](https://github.com/py-pdf/pypdf) from 6.7.5 to 6.9.1.
- [Release notes](https://github.com/py-pdf/pypdf/releases)
- [Changelog](https://github.com/py-pdf/pypdf/blob/main/CHANGELOG.md)
- [Commits](py-pdf/pypdf@6.7.5...6.9.1)

---
updated-dependencies:
- dependency-name: pypdf
  dependency-version: 6.9.1
  dependency-type: direct:production
...

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

Author: dependabot[bot]

poetry.lock

@@ -23,7 +23,7 @@ langchain = "^0.3.21"
 langchain-community = "^0.3.29"
 langchain-openai = "^0.3.11"
 aidial-sdk = {extras = ["telemetry"], version = "^0.21.0"}
-pypdf = "^6.6.0"
+pypdf = "^6.9.1"
 rank-bm25 = "0.2.2"
 sentence-transformers = {version = "3.3.1", extras = ["openvino"]}
 tiktoken = "^0.7.0"