Fix fixtures

Author: sebmarkbage

fixtures/fizz-ssr-browser/index.html

@@ -17,6 +17,7 @@ <h1>Fizz Example</h1>
       </p>
     </div>
     <script src="../../build/node_modules/react/umd/react.development.js"></script>
+    <script src="../../build/node_modules/react-dom/umd/react-dom.development.js"></script>
     <script src="../../build/node_modules/react-dom/umd/react-dom-server.browser.development.js"></script>
     <script src="https://unpkg.com/babel-standalone@6/babel.js"></script>
     <script type="text/babel">

fixtures/flight-browser/index.html

@@ -94,11 +94,12 @@ <h1>{model.title}</h1>
 
       function renderResult(data) {
         let container = document.getElementById('container');
-        ReactDOM.render(
+        ReactDOM.createRoot(
+          container
+        ).render(
           <Suspense fallback="Loading...">
             <Shell data={data} />
           </Suspense>,
-          container
         );
       }
     </script>