deleteMetaData method
Deletes a meta data.
Implementation
Future<void> deleteMetaData(String key) async {
  sbLog.i(StackTrace.current, 'key: $key');
  checkUnsupportedAction();
  if (key.isEmpty) {
    throw InvalidParameterException();
  }
  final ts = await chat.apiClient.send<int>(
    ChannelMetaDataDeleteRequest(
      chat,
      channelType: channelType,
      channelUrl: channelUrl,
      key: key,
    ),
  );
  final cachedMetaData =
      chat.channelCache.find<MetaDataCache>(channelKey: channelUrl) ??
          MetaDataCache<String>(
            channelType: channelType,
            channelUrl: channelUrl,
            timestamp: ts,
          );
  cachedMetaData.removeWithKey(key, ts);
  cachedMetaData.saveToCache(chat);
}