Bump pypdf from 6.9.2 to 6.10.1 in /backend

Bumps [pypdf](https://github.com/py-pdf/pypdf) from 6.9.2 to 6.10.1.
- [Release notes](https://github.com/py-pdf/pypdf/releases)
- [Changelog](https://github.com/py-pdf/pypdf/blob/main/CHANGELOG.md)
- [Commits](py-pdf/pypdf@6.9.2...6.10.1)

---
updated-dependencies:
- dependency-name: pypdf
  dependency-version: 6.10.1
  dependency-type: direct:production
...

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

Author: dependabot[bot]

backend/requirements.txt

@@ -8,4 +8,4 @@ openpyxl==3.1.5
 grequests==0.7.0
 pyclustering==0.10.1.2
 polyline==2.0.4
-pypdf==6.9.2
+pypdf==6.10.1