chore(deps): update dependency ember-cli to v3.28.6

Author: renovate[bot]

package.json

@@ -46,7 +46,7 @@
     "babel-eslint": "10.1.0",
     "broccoli-asset-rev": "3.0.0",
     "ember-auto-import": "1.11.3",
-    "ember-cli": "3.26.1",
+    "ember-cli": "3.28.6",
     "ember-cli-dependency-checker": "3.2.0",
     "ember-cli-inject-live-reload": "2.1.0",
     "ember-cli-sri": "2.1.1",