replace makeFilteredResponse proxy

lib/fetch/response.js

@@ -371,21 +371,14 @@ function makeNetworkError (reason) {
 }
 
 function makeFilteredResponse (response, state) {
-  state = {
-    internalResponse: response,
-    ...state
-  }
-
-  return new Proxy(response, {
-    get (target, p) {
-      return p in state ? state[p] : target[p]
-    },
-    set (target, p, value) {
-      assert(!(p in state))
-      target[p] = value
-      return true
-    }
-  })
+  // https://fetch.spec.whatwg.org/#concept-filtered-response
+  // A filtered response has a corresponding internalResponse, which is its
+  // response. However, a key accessed in the response object must also be
+  // available in its internal response (and vice versa).
+  const cloned = cloneResponse(response)
+  Object.assign(response, { internalResponse: cloned }, state)
+
+  return response
 }
 
 // https://fetch.spec.whatwg.org/#concept-filtered-response