Build(deps-dev): Bump @ember/string from 3.1.1 to 4.0.0 (#27750)

Bumps [@ember/string](https://github.com/emberjs/ember-string) from 3.1.1 to 4.0.0.
- [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/commits)

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

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

app/assets/javascripts/discourse/package.json

@@ -41,7 +41,7 @@
     "@ember/legacy-built-in-components": "^0.5.0",
     "@ember/optional-features": "^2.1.0",
     "@ember/render-modifiers": "^2.1.0",
-    "@ember/string": "^3.1.1",
+    "@ember/string": "^4.0.0",
     "@ember/test-helpers": "^3.3.0",
     "@embroider/compat": "^3.5.6",
     "@embroider/core": "^3.4.14",