Update recommendations for HTTP server packages

sdk/lib/io/http.dart

Index: sdk/lib/io/http.dart
diff --git a/sdk/lib/io/http.dart b/sdk/lib/io/http.dart
index d61835cbf311e6c55c7c62e2d57e16fb4532ad3f..f8eacb7819fa761e57fbd6a2bf4f55bbfaa7b328 100644
--- a/sdk/lib/io/http.dart
+++ b/sdk/lib/io/http.dart
@@ -149,7 +149,7 @@ abstract class HttpStatus {
  * about the streaming qualities of an HttpServer.
  * Pausing the subscription of the stream, pauses at the OS level.
  *
- * * The [http_server](https://pub.dartlang.org/packages/http_server)
+ * * The [shelf](https://pub.dartlang.org/packages/shelf)
  * package on pub.dartlang.org contains a set of high-level classes that,
  * together with this class, makes it easy to provide content through HTTP
  * servers.