Use unstable embroider for test-app

Author: NullVoxPopuli

pnpm-lock.yaml

@@ -47,10 +47,10 @@
     "@ember/optional-features": "^2.0.0",
     "@ember/string": "^3.0.1",
     "@ember/test-helpers": "^2.9.3",
-    "@embroider/compat": "^2.1.1",
-    "@embroider/core": "^2.1.1",
-    "@embroider/test-setup": "^2.1.1",
-    "@embroider/webpack": "^2.1.1",
+    "@embroider/compat": "2.1.2-unstable.df7f441",
+    "@embroider/core": "2.1.2-unstable.df7f441",
+    "@embroider/test-setup": "2.1.2-unstable.df7f441",
+    "@embroider/webpack": "2.1.2-unstable.df7f441",
     "@glint/core": "^1.0.0-beta.3",
     "@glint/environment-ember-loose": "^1.0.0-beta.3",
     "@glint/environment-ember-template-imports": "^1.0.0-beta.3",