Revert "Use duplex: 'half'"

This reverts commit 9a2ef7e.

src/Fetch/Core/Request.js

@@ -1,6 +1,6 @@
 export function _unsafeNew(url, options) {
   try {
-    return new Request(url, { ...options, duplex: 'half' });
+    return new Request(url, options);
   } catch (e) {
     console.error(e);
     throw e;