Bump ghostscript from 0.7 to 0.8.1 in /docs

Bumps [ghostscript](https://gitlab.com/pdftools/python-ghostscript) from 0.7 to 0.8.1.
- [Release notes](https://gitlab.com/pdftools/python-ghostscript/tags)
- [Changelog](https://gitlab.com/pdftools/python-ghostscript/blob/develop/CHANGES.txt)
- [Commits](https://gitlab.com/pdftools/python-ghostscript/compare/v0.7...v0.8.1)

---
updated-dependencies:
- dependency-name: ghostscript
  dependency-version: 0.8.1
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

docs/requirements.txt

@@ -2,7 +2,7 @@ sphinx==8.1.3
 sphinx-book-theme>=1.0.1
 sphinx-click==6.0.0
 myst_parser==4.0.0
-ghostscript==0.7
+ghostscript==0.8.1
 opencv-python-headless==4.11.0.86
 matplotlib==3.10.1
 accessible-pygments==0.0.5