Bump sass in /src/sphinx_antsibull_ext/css in the npm group (#453)

Bumps the npm group in /src/sphinx_antsibull_ext/css with 1 update: [sass](https://github.com/sass/dart-sass).


Updates `sass` from 1.98.0 to 1.99.0
- [Release notes](https://github.com/sass/dart-sass/releases)
- [Changelog](https://github.com/sass/dart-sass/blob/main/CHANGELOG.md)
- [Commits](sass/dart-sass@1.98.0...1.99.0)

---
updated-dependencies:
- dependency-name: sass
  dependency-version: 1.99.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: npm
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

src/sphinx_antsibull_ext/css/package-lock.json

@@ -4,6 +4,6 @@
     "cssnano": "^7.1.4",
     "postcss": "^8.5.8",
     "postcss-cli": "^11.0.1",
-    "sass": "^1.98.0"
+    "sass": "^1.99.0"
   }
 }