build(deps): bump ocrmypdf from 16.12.0 to 16.13.0 in /pdf

Bumps [ocrmypdf](https://github.com/ocrmypdf/OCRmyPDF) from 16.12.0 to 16.13.0.
- [Release notes](https://github.com/ocrmypdf/OCRmyPDF/releases)
- [Changelog](https://github.com/ocrmypdf/OCRmyPDF/blob/main/docs/release_notes.md)
- [Commits](ocrmypdf/OCRmyPDF@v16.12.0...v16.13.0)

---
updated-dependencies:
- dependency-name: ocrmypdf
  dependency-version: 16.13.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

pdf/requirements.txt

@@ -1 +1 @@
-ocrmypdf==16.12.0
+ocrmypdf==16.13.0