fix SseLineSubscriber will not request after default 256 request

Author: taobaorun

mcp/src/main/java/io/modelcontextprotocol/client/transport/ResponseSubscribers.java

@@ -141,7 +141,7 @@ protected void hookOnSubscribe(Subscription subscription) {
 
 		@Override
 		protected void hookOnNext(String line) {
-
+			request(1);
 			if (line.isEmpty()) {
 				// Empty line means end of event
 				if (this.eventBuilder.length() > 0) {