build(deps): Bump css-tree from 2.3.0 to 2.3.1 (ember-cli#1707)

Bumps [css-tree](https://github.com/csstree/csstree) from 2.3.0 to 2.3.1.
- [Release notes](https://github.com/csstree/csstree/releases)
- [Changelog](https://github.com/csstree/csstree/blob/master/CHANGELOG.md)
- [Commits](csstree/csstree@v2.3.0...v2.3.1)

---
updated-dependencies:
- dependency-name: css-tree
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

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

yarn.lock

@@ -2065,9 +2065,9 @@ crypto-random-string@^4.0.0:
     type-fest "^1.0.1"
 
 css-tree@^2.0.4:
-  version "2.3.0"
-  resolved "https://registry.yarnpkg.com/css-tree/-/css-tree-2.3.0.tgz#a0122cbc85305576df92ac528fb079c8217a15b2"
-  integrity sha512-1rg0LiK2MFi4R3/lVvnRokEWTZb30ljSAe5x+0HHkZ+OqZaAeiP8g8Eh91VmkyCtQn9vMgQRiaTDYgLBt+2Qyw==
+  version "2.3.1"
+  resolved "https://registry.yarnpkg.com/css-tree/-/css-tree-2.3.1.tgz#10264ce1e5442e8572fc82fbe490644ff54b5c20"
+  integrity sha512-6Fv1DV/TYw//QF5IzQdqsNDjx/wc8TrMBZsqjL9eW01tWb7R7k/mq+/VXfJCl7SoD5emsJop9cOByJZfs8hYIw==
   dependencies:
     mdn-data "2.0.30"
     source-map-js "^1.0.1"