Remove non-functional Thread.sleep(50) from async handler

The sleep doesn't reproduce the flake — it delays the Future body execution,
not the gap between span finish and Scala continuation cleanup. The race
window is nanoseconds and only manifests under extreme CI load (>20s OS
preemption). The .recover fix eliminates the race by design: converting the
failed Future to a successful one ensures the span is finished deterministically
before the HTTP response is sent.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: bm1549

dd-java-agent/instrumentation/pekko/pekko-http-1.0/src/baseTest/scala/PekkoHttpTestWebServer.scala

@@ -274,10 +274,6 @@ object PekkoHttpTestWebServer {
       ec: ExecutionContext
   ): HttpRequest => Future[HttpResponse] = { request =>
     Future {
-      // Deterministic reproduction: delay async execution to widen the race window
-      // between Future continuation cleanup and span completion. Without .recover,
-      // this delay makes the failed-Future trace-drop race condition trigger reliably.
-      Thread.sleep(50)
       syncHandler(request)
     }.recover { case e: Exception =>
       // Recover from exceptions to return a proper HTTP response instead of a