Add QA test coverage for lock file with `refactor_blob_viewer` enabled

We need to add test coverage for the lock file button with the refactor_blob_viewer enabled.

See #330406 (comment 631715143) for context

Please run package-and-qa with the refactor_blob_viewer feature flag enabled when the work is complete, but before the flag is enabled on Staging or GitLab.com, to confirm that the QA test of the lock button passes.