test: deflake test-net-throttle

Sometimes the test completes with only two data chunks received on the
client.

Fixes: nodejs#40507

test/parallel/test-net-throttle.js

@@ -84,5 +84,5 @@ server.listen(0, () => {
 
 process.on('exit', () => {
   assert.strictEqual(chars_recved, totalLength);
-  assert.strictEqual(npauses > 2, true);
+  assert.ok(npauses > 1, `npauses = ${npauses}`);
 });