Changed experimental features documentation back to __experimental

Author: Alexander Botteram

docs/coding-guidelines.md

@@ -88,13 +88,13 @@ import VisualEditor from '../visual-editor';
 
 ### Experimental APIs
 
-Exposed APIs that are still being tested, discussed and are subject to change should be prefixed with `experimental__`, until they are finalized. This is meant to discourage developers from relying on the API, because it might be removed or changed in the (near) future.
+Exposed APIs that are still being tested, discussed and are subject to change should be prefixed with `__experimental`, until they are finalized. This is meant to discourage developers from relying on the API, because it might be removed or changed in the (near) future.
 
 Example:
 
 ```js
 export {
-	internalApi as experimental__exposedApi
+	internalApi as __experimentalExposedApi
 } from './internalApi.js';
 ```