Make open editor icon size non-shrink in error overlay (#55273)

In error overlay when the error trace file path is too long, the open editor icon on the right side get shrinked to very small. Mark it as `flex-shrink: 0` to avoid the unexpected size change

### After

![image](https://github.com/vercel/next.js/assets/4800338/31d93520-ee82-4867-97b3-9e22e5f71da7)


### Before

![image](https://github.com/vercel/next.js/assets/4800338/57c27636-b9e6-4e1d-b68b-0247dbd882cd)

packages/next/src/client/components/react-dev-overlay/internal/container/RuntimeError/index.tsx

@@ -162,6 +162,7 @@ export const styles = css`
     width: auto;
     height: var(--size-font-small);
     margin-left: var(--size-gap);
+    flex-shrink: 0;
 
     display: none;
   }