Function: force_witness

Allows any call to be forcefully dispatched by the root, provided that

• The epoch_index has not expired.

• The call hash and epoch_index have at least one registered vote:

  ensure!(Votes::::contains_key(epoch_index, call_hash), Error::::InvalidEpoch);

The function does not check that the hash is not registered in CallHashExecuted pallet storage to prevent replays; however, it does insert the hash there to record that the call has been made. So, the function may replay a call, but it prevents other methods of executing a call (directly witnessing and executing, or scheduling — ideally) from executing in the future.