Fix hidden copy button on production build for text fields (#12099)

Fixes #11762

The `copy-button` classname from scalar was overwritting the style of
our copy button. It only happened in production build and not with `npx
nx run twenty-front:start` so it was quite hard to catch. Thanks
@charlesBochet for finding the root cause.

- Removed `copy-button` classname since it was unused
- Added `?inline` when importing scalar css to have inline css

Before:
<img width="210" alt="Capture d’écran 2025-05-16 à 17 43 50"
src="https://github.com/user-attachments/assets/7256b5e6-0b61-4590-a4de-d6b28ab2b4ed"
/>

After:
<img width="230" alt="Capture d’écran 2025-05-16 à 17 43 32"
src="https://github.com/user-attachments/assets/a763172b-0566-413d-bbdd-470f28097ae4"
/>

packages/twenty-front/src/modules/settings/playground/components/RestPlayground.tsx

@@ -31,7 +31,7 @@ const StyledContainer = styled.div`
 
 const ApiReferenceReact = lazy(() =>
   import('@scalar/api-reference-react').then((module) => {
-    import('@scalar/api-reference-react/style.css');
+    import('@scalar/api-reference-react/style.css?inline');
     return {
       default: module.ApiReferenceReact,
     };