message: Forbid redaction of encryption events
  Redacting m.room.encryption events will leave the room in a broken
  state, and so we shouldn't allow the user to do this.
diff: @@ -78,8 +78,10 @@ export default class MessageContextMenu extends React.Component {
  // We explicitly decline to show the redact option on ACL events as it has a potential
  // to obliterate the room - https://github.com/matrix-org/synapse/issues/4042
  + // Similarly for encryption events, since redacting them "breaks everything"
  const canRedact = room.currentState.maySendRedactionForEvent(this.props.mxEvent, cli.credentials.userId)
  - && this.props.mxEvent.getType() !== EventType.RoomServerAcl;
  + && this.props.mxEvent.getType() !== EventType.RoomServerAcl
  + && this.props.mxEvent.getType() !== EventType.RoomEncryption;
  let canPin = room.currentState.mayClientSendStateEvent('m.room.pinned_events', cli);
  // HACK: Intentionally say we can't pin if the user doesn't want to use the functionality
  