Bump sass from 1.90.0 to 1.91.0 in /ext/sass (#326)

Bumps [sass](https://github.com/sass/dart-sass) from 1.90.0 to 1.91.0.
- [Release notes](https://github.com/sass/dart-sass/releases)
- [Changelog](https://github.com/sass/dart-sass/blob/main/CHANGELOG.md)
- [Commits](sass/dart-sass@1.90.0...1.91.0)

---
updated-dependencies:
- dependency-name: sass
  dependency-version: 1.91.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

ext/sass/package.json

@@ -1,5 +1,5 @@
 {
   "dependencies": {
-    "sass": "1.90.0"
+    "sass": "1.91.0"
   }
 }