Build(deps): Bump pypdf from 5.6.0 to 6.0.0 in /backend in the pip group across 1 directory (#168)

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

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


Updates `pypdf` from 5.6.0 to 6.0.0
- [Release notes](https://github.com/py-pdf/pypdf/releases)
- [Changelog](https://github.com/py-pdf/pypdf/blob/main/CHANGELOG.md)
- [Commits](py-pdf/pypdf@5.6.0...6.0.0)

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

backend/requirements.txt

@@ -16,7 +16,7 @@ sphinxcontrib-mermaid==0.9.2
 sphinx-book-theme==1.1.3
 sphinx-copybutton==0.5.2
 sphinx-external-toc==1.0.1
-pypdf==5.6.0
+pypdf==6.0.0
 unstructured==0.15.1
 nltk==3.9.1
 huggingface_hub[cli]==0.24.6