fix: page response missing CSP and Link headers when return promise in load (#11801)

Author: 0x221A

.changeset/tidy-timers-perform.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+fix: page response missing CSP and Link headers when return promise in `load`

packages/kit/src/runtime/server/page/render.js

@@ -511,9 +511,7 @@ export async function render_response({
 					type: 'bytes'
 				}),
 				{
-					headers: {
-						'content-type': 'text/html'
-					}
+					headers
 				}
 			);
 }