Bump sybil from 9.0.0 to 9.1.0

Bumps [sybil](https://github.com/simplistix/sybil) from 9.0.0 to 9.1.0.
- [Changelog](https://github.com/simplistix/sybil/blob/master/CHANGELOG.rst)
- [Commits](simplistix/sybil@9.0.0...9.1.0)

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

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

Author: dependabot[bot]

pyproject.toml

@@ -73,7 +73,7 @@ optional-dependencies.dev = [
     "sphinx-lint==1.0.0",
     "sphinx-substitution-extensions==2025.2.19",
     "sphinxcontrib-spelling==8.0.1",
-    "sybil==9.0.0",
+    "sybil==9.1.0",
     "types-requests==2.32.0.20241016",
     "vulture==2.14",
     "vws-python-mock==2024.8.30",