Re-enable React strict mode

src/main.tsx

@@ -11,6 +11,7 @@ Please see LICENSE in the repository root for full details.
 // dependency references.
 import "matrix-js-sdk/lib/browser-index";
 
+import { StrictMode } from "react";
 import { createRoot } from "react-dom/client";
 import "./index.css";
 import { logger } from "matrix-js-sdk/lib/logger";
@@ -59,9 +60,9 @@ if (fatalError !== null) {
 Initializer.initBeforeReact()
   .then(() => {
     root.render(
-      // <StrictMode>
-      <App vm={new AppViewModel()} />,
-      // </StrictMode>,
+      <StrictMode>
+        <App vm={new AppViewModel()} />,
+      </StrictMode>,
     );
   })
   .catch((e) => {