Update dependency pypdf to v6.3.0 (#10)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| [pypdf](https://github.com/py-pdf/pypdf) ([changelog](https://pypdf.readthedocs.io/en/latest/meta/CHANGELOG.html)) | minor | `==6.1.3` -> `==6.3.0` |

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Reviewed-on: #10
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Co-committed-by: Renovate Bot <renovate@git.tidoni-sky.ddnss.de>

requirements.txt

@@ -1,6 +1,6 @@
 flask==3.1.2
 gunicorn==23.0.0
-pypdf==6.1.3
+pypdf==6.3.0
 
 # For testing
 pytest==8.4.2