Update pypdf requirement in /topic/machine-learning/langchain

Updates the requirements on [pypdf](https://github.com/py-pdf/pypdf) to permit the latest version.
- [Release notes](https://github.com/py-pdf/pypdf/releases)
- [Changelog](https://github.com/py-pdf/pypdf/blob/main/CHANGELOG.md)
- [Commits](py-pdf/pypdf@v1.17...6.0.0)

---
updated-dependencies:
- dependency-name: pypdf
  dependency-version: 6.0.0
  dependency-type: direct:production
...

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

Author: dependabot[bot]

topic/machine-learning/langchain/requirements.txt

@@ -8,7 +8,7 @@ langchain-openai<0.4
 langchain-text-splitters<0.4
 langgraph<0.7
 pueblo[cli,nlp]>=0.0.10
-pypdf<6
+pypdf<7
 python-dotenv<2
 requests<3
 requests-cache<2