Update BB primer section and gif

Primer needs to be updated to reflect the behaviour of the bus qubit in BB qRAM. It does not, in fact, perform the resetting of the qutrits back to the |wait> state, but rather exits on its own. The qutrits are to be reset by the address qubits that were sent in from the start - they "leave" the system and perform the inverse unitary operation on their way out.