fix: handle Headers in RedirectHandler

Author: iiAku

lib/handler/redirect-handler.js

@@ -227,9 +227,10 @@ function cleanRequestHeaders (headers, removeContent, unknownOrigin) {
       }
     }
   } else if (headers && typeof headers === 'object') {
-    for (const key of Object.keys(headers)) {
+    const entries = headers instanceof Headers ? headers.entries() : Object.entries(headers)
+    for (const [key, value] of entries) {
       if (!shouldRemoveHeader(key, removeContent, unknownOrigin)) {
-        ret.push(key, headers[key])
+        ret.push(key, value)
       }
     }
   } else {