While this class syncs up Studio-based modal editor styling, I'm weary about giving it this specific .modal-actions class for all other editing cases outside of Studio. I'd like to use a more flexbile UI-based class, like xblock-edit-actions.

Given that this fix needs to get in shortly, I'm happy to have this done in a follow-up PR (with a companion PR on the edx-platform/Studio) side.