Remove and add members can not pass initiator

[erdtsieck]

The initiator that removed the member is ignored in the request to update channel.

This also leads to member.removed events (on SQS) not containing the initiator of the action.

In the code below initiatorId is ignored

var memberDeletedMessage = "some message";
var messageRequest = new MessageRequest() { 
    Type = MessageRequestType.System, 
    Text = memberDeletedMessage, 
    UserId = initiatorId 
};

await _streamClientFactory.GetChannelClient()
    .RemoveMembersAsync(channelType, channelId, new List<string> { memberToDeleteUserId }, messageRequest);