Bump furo from 2025.9.25 to 2025.12.19 in the dependencies group

Bumps the dependencies group with 1 update: [furo](https://github.com/pradyunsg/furo).


Updates `furo` from 2025.9.25 to 2025.12.19
- [Release notes](https://github.com/pradyunsg/furo/releases)
- [Changelog](https://github.com/pradyunsg/furo/blob/main/docs/changelog.md)
- [Commits](pradyunsg/furo@2025.09.25...2025.12.19)

---
updated-dependencies:
- dependency-name: furo
  dependency-version: 2025.12.19
  dependency-type: direct:development
  update-type: version-update:semver-minor
  dependency-group: dependencies
...

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

Author: dependabot[bot]

pyproject.toml

@@ -71,7 +71,7 @@ dev = [
 
 # Docs are always built on a specific Python version; see RTD and tox config files.
 docs = [
-    "furo == 2025.9.25",
+    "furo == 2025.12.19",
     "pyenchant == 3.3.0",
     "sphinx == 8.2.3",
     "sphinx_tabs == 3.4.7",