Bump ember-cli from 3.25.0 to 3.28.4

Bumps [ember-cli](https://github.com/ember-cli/ember-cli) from 3.25.0 to 3.28.4.
- [Release notes](https://github.com/ember-cli/ember-cli/releases)
- [Changelog](https://github.com/ember-cli/ember-cli/blob/master/CHANGELOG.md)
- [Commits](ember-cli/ember-cli@v3.25.0...v3.28.4)

---
updated-dependencies:
- dependency-name: ember-cli
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

package.json

@@ -59,7 +59,7 @@
     "@embroider/test-setup": "^0.41.0",
     "babel-eslint": "^10.1.0",
     "codeclimate-test-reporter": "^0.5.0",
-    "ember-cli": "^3.25.0",
+    "ember-cli": "^3.28.4",
     "ember-cli-addon-docs": "^0.10.0",
     "ember-cli-addon-docs-yuidoc": "^0.2.4",
     "ember-cli-dependency-checker": "^3.0.0",