Bump grunt-sass from 3.1.0 to 4.0.0 (fixes #239)

Bumps [grunt-sass](https://github.com/sindresorhus/grunt-sass) from 3.1.0 to 4.0.0.
- [Release notes](https://github.com/sindresorhus/grunt-sass/releases)
- [Commits](sindresorhus/grunt-sass@v3.1.0...v4.0.0)

---
updated-dependencies:
- dependency-name: grunt-sass
  dependency-type: direct:development
  update-type: version-update:semver-major
...

Change-Id: Icea55710a593444e8aab127372c8b668857658c4
Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

package.json

@@ -16,7 +16,7 @@
     "grunt-contrib-copy": "^1.0.0",
     "grunt-contrib-requirejs": "^1.0.0",
     "grunt-contrib-watch": "^1.1.0",
-    "grunt-sass": "^3.1.0",
+    "grunt-sass": "^4.0.0",
     "grunt-shell": "^4.0.0",
     "grunt-terser": "^2.0.0",
     "imagemin": "^8.0.1",