Fix test flake in js-rpc-socket-test, introduced in #2764.

src/workerd/api/tests/js-rpc-test.js

@@ -950,8 +950,13 @@ export let disposal = {
       let counter = new MyCounter(3);
       await env.MyService.leakButReturnPlainObject(counter);
 
-      // Give a chance for disposal to happen.
-      await scheduler.wait(10);
+      // Give a chance for disposal to happen. When running with a real socket, this involves
+      // non-deterministic scheduling, and it can be relatively slower when running under ASAN,
+      // QEMU, etc. so we'll try to dynamically adjust how much time we wait, up to 10s.
+      for (let i = 0; i < 1000; i++) {
+        if (counter.disposed) break;
+        await scheduler.wait(10);
+      }
 
       // It should have happened! A call that returns a plain object should NOT
       // require disposal to clean up its context!