test: fix flaky test-http2-close-while-writing

Use stream.once() instead of stream.on() for the 'data' event
handler to prevent multiple calls when receiving large data chunks.
The test sends 64KB of data which may arrive in multiple chunks,
causing the destroy callback to fire multiple times and leading
to intermittent timeouts on macOS.

Refs: nodejs/reliability#1459

Author: mcollina

test/parallel/test-http2-close-while-writing.js

@@ -24,7 +24,7 @@ let client_stream;
 server.on('session', common.mustCall(function(session) {
   session.on('stream', common.mustCall(function(stream) {
     stream.resume();
-    stream.on('data', function() {
+    stream.once('data', function() {
       this.write(Buffer.alloc(1));
       process.nextTick(() => client_stream.destroy());
     });