[deps] Update pypandoc requirement from ~=1.15 to ~=1.16

Updates the requirements on [pypandoc](https://github.com/JessicaTegner/pypandoc) to permit the latest version.
- [Release notes](https://github.com/JessicaTegner/pypandoc/releases)
- [Changelog](https://github.com/JessicaTegner/pypandoc/blob/master/release.md)
- [Commits](JessicaTegner/pypandoc@v1.15...v1.16.2)

---
updated-dependencies:
- dependency-name: pypandoc
  dependency-version: 1.16.2
  dependency-type: direct:production
...

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

Author: dependabot[bot]

requirements.txt

@@ -2,7 +2,7 @@ sphinx~=8.0.2
 sphinxawesome-theme~=5.3.2
 svglib
 rst2pdf
-pypandoc~=1.15
+pypandoc~=1.16
 pypandoc_binary~=1.15
 sphinxcontrib-jquery
 sphinx-notfound-page