Update dependency ember-cli to v6

Author: renovate[bot]

packages/test-app/package.json

@@ -32,7 +32,7 @@
     "@glimmer/component": "1.1.2",
     "broccoli-asset-rev": "3.0.0",
     "ember-auto-import": "2.10.0",
-    "ember-cli": "4.12.3",
+    "ember-cli": "6.8.0",
     "ember-cli-babel": "8.2.0",
     "ember-cli-dependency-checker": "3.3.3",
     "ember-cli-htmlbars": "6.3.0",