fix: ssr method expects rawBody instead of body

closes #1143

Author: ivoreis

.changeset/warm-jars-move.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/adapter-vercel': patch
+---
+
+fix body parsing

packages/adapter-vercel/files/entry.js

@@ -12,7 +12,7 @@ export default async (req, res) => {
 		headers: req.headers,
 		path: pathname,
 		query: searchParams,
-		body: await getRawBody(req)
+		rawBody: await getRawBody(req)
 	});
 
 	if (rendered) {