chore(deps-dev): update pypdf requirement from >=4.0 to >=6.12.1 (#79)

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@4.0.0...6.12.1)

---
updated-dependencies:
- dependency-name: pypdf
  dependency-version: 6.10.2
  dependency-type: direct:development
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Pratyush Sharma <56130065+pratyush618@users.noreply.github.com>

Author: dependabot[bot]

pyproject.toml

@@ -50,7 +50,7 @@ dev = [
     "pytest>=8.0",
     "pytest-asyncio>=0.24",
     "pytest-benchmark>=4.0",
-    "pypdf>=4.0",
+    "pypdf>=6.12.1",
     "pdfplumber>=0.10",
     "mypy>=1.8",
     "ruff>=0.3",