Bump ember-cli from 3.12.0 to 3.28.4

Bumps [ember-cli](https://github.com/ember-cli/ember-cli) from 3.12.0 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@v3.12.0...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

@@ -106,7 +106,7 @@
     "common-tags": "^1.8.0",
     "core-js": "^2.6.5",
     "dag-map": "^2.0.2",
-    "ember-cli": "^3.12.0",
+    "ember-cli": "^3.28.4",
     "ember-cli-blueprint-test-helpers": "^0.19.2",
     "ember-cli-browserstack": "^2.0.1",
     "ember-cli-dependency-checker": "^3.2.0",