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

Author: renovate[bot]

package.json

@@ -54,7 +54,7 @@
     "@glimmer/tracking": "^1.0.4",
     "babel-eslint": "10.1.0",
     "broccoli-asset-rev": "3.0.0",
-    "ember-cli": "3.28.0",
+    "ember-cli": "3.28.6",
     "ember-cli-dependency-checker": "3.2.0",
     "ember-cli-deprecation-workflow": "1.0.1",
     "ember-cli-inject-live-reload": "2.1.0",