fix: external rewrite for streaming (#791)

* fix external rewrite for streaming

* changeset

Author: sommeeeer

.changeset/heavy-moles-share.md

@@ -0,0 +1,5 @@
+---
+"@opennextjs/aws": patch
+---
+
+fix external rewrite for streaming

packages/open-next/src/core/requestHandler.ts

@@ -138,7 +138,7 @@ export async function openNextHandler(
               origin: false,
               initialURL: internalEvent.url,
             },
-            headers,
+            routingResult.headers,
             options.streamCreator,
           );
           response.statusCode = routingResult.statusCode;