message: Fix race condition in `AccountSettingsHandler` local echo
  Should fix
diff: @@ -165,8 +165,8 @@ export default class AccountSettingsHandler extends MatrixClientBackedSettingsHa
  content[field] = value;
  - await this.client.setAccountData(eventType, content);
  -
  + // Attach a deferred *before* setting the account data to ensure we catch any requests
  + // which race between different lines.
  const deferred = defer<void>();
  const handler = (event: MatrixEvent) => {
  if (event.getType() !== eventType || event.getContent()[field] !== value) return;
  @@ -175,6 +175,8 @@ export default class AccountSettingsHandler extends MatrixClientBackedSettingsHa
  };
  this.client.on(ClientEvent.AccountData, handler);
  + await this.client.setAccountData(eventType, content);
  +
  await deferred.promise;
  }
  