remove hard-coded json content-type for streaming http output

There was a stale assumption that streaming output from a channel would
always be json.
This commit removes that code, allowing Content-Type to appropriately be
set like other, non-channel-streaming commands.

License: MIT
Signed-off-by: Cayman Nava <caymannava@gmail.com>

commands/http/handler.go

@@ -224,13 +224,8 @@ func sendResponse(w http.ResponseWriter, r *http.Request, res cmds.Response, req
 		_, isChan = res.Output().(<-chan interface{})
 	}
 
-	streamChans, _, _ := req.Option("stream-channels").Bool()
 	if isChan {
 		h.Set(channelHeader, "1")
-		if streamChans {
-			// streaming output from a channel will always be json objects
-			mime = applicationJson
-		}
 	}
 
 	if mime != "" {