Clean up ExtendedSpanBuilder call chain in HTTP Server Example (#542)

Author: illenko

http/src/main/java/io/opentelemetry/example/http/HttpServer.java

@@ -48,15 +48,12 @@ private static class HelloHandler implements HttpHandler {
 
     @Override
     public void handle(HttpExchange exchange) throws IOException {
-      // TODO (trask) clean up chaining after
-      // https://github.com/open-telemetry/opentelemetry-java/pull/6514
-      ((ExtendedSpanBuilder)
-              ((ExtendedSpanBuilder) tracer.spanBuilder("GET /"))
-                  .setParentFrom(
-                      openTelemetry.getPropagators(),
-                      exchange.getRequestHeaders().entrySet().stream()
-                          .collect(Collectors.toMap(Map.Entry::getKey, e -> e.getValue().get(0))))
-                  .setSpanKind(SpanKind.SERVER))
+      ((ExtendedSpanBuilder) tracer.spanBuilder("GET /"))
+          .setParentFrom(
+              openTelemetry.getPropagators(),
+              exchange.getRequestHeaders().entrySet().stream()
+                  .collect(Collectors.toMap(Map.Entry::getKey, e -> e.getValue().get(0))))
+          .setSpanKind(SpanKind.SERVER)
           .startAndRun(
               () -> {
                 // Set the Semantic Convention