Build(deps): Bump @ember/string in /app/assets/javascripts (#21569)

Bumps [@ember/string](https://github.com/emberjs/ember-string) from 3.0.1 to 3.1.0.
- [Release notes](https://github.com/emberjs/ember-string/releases)
- [Changelog](https://github.com/emberjs/ember-string/blob/master/CHANGELOG.md)
- [Commits](https://github.com/emberjs/ember-string/compare/v3.0.1...v3.1.0)

---
updated-dependencies:
- dependency-name: "@ember/string"
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

app/assets/javascripts/discourse-widget-hbs/package.json

@@ -23,7 +23,7 @@
   "devDependencies": {
     "@babel/core": "^7.21.8",
     "@ember/optional-features": "^2.0.0",
-    "@ember/string": "^3.0.1",
+    "@ember/string": "^3.1.0",
     "@embroider/test-setup": "^2.1.1",
     "@glimmer/component": "^1.1.2",
     "@glimmer/syntax": "^0.84.3",