Fix assertion in mocks_helper_spec.js
What does this MR do?
Fix a broken assertion in spec/frontend/mocks/mocks_helper_spec.js.
This is necessary for https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/31967.
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Fix a broken assertion in spec/frontend/mocks/mocks_helper_spec.js.
This is necessary for https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/31967.