Update dependency ember-cli to ~6.8.0

Author: renovate[bot]

package.json

@@ -124,7 +124,7 @@
     "concurrently": "^9.2.1",
     "coveralls": "^3.0.9",
     "ember-a11y-testing": "^7.1.0",
-    "ember-cli": "~6.7.0",
+    "ember-cli": "~6.8.0",
     "ember-cli-blueprint-test-helpers": "^0.19.2",
     "ember-cli-clean-css": "^3.0.0",
     "ember-cli-code-coverage": "^1.0.3",