build(deps): bump pypdf in the pip group across 1 directory

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


Updates `pypdf` from 6.8.0 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@6.8.0...6.9.1)

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

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

Author: dependabot[bot]

pyproject.toml

@@ -52,7 +52,7 @@ dependencies = [
     "xlrd==2.0.2",
     "xlwt==1.3.0",
     "pymupdf==1.26.3",
-    "pypdf==6.8.0",
+    "pypdf==6.9.1",
     "pydub==0.25.1",
     "pysilk==0.0.1",
     "gunicorn==23.0.0",