fix(backend): Fix auth helpers tests and remove unnecessary comment

- Fixed 3 failing tests in helpers_test.py that were incorrectly trying
  to mock 'backend.api.auth.helpers.get_openapi' (which doesn't exist)
- Tests now properly mock the app's openapi method directly
- Removed unnecessary comment in dependabot.yml per review feedback

.github/dependabot.yml

@@ -1,7 +1,5 @@
 version: 2
 updates:
-  # autogpt_libs merged into backend (OPEN-2998)
-
   # backend (Poetry project)
   - package-ecosystem: "pip"
     directory: "autogpt_platform/backend"