Remove storybook-addon-mock from Storybook configuration

Co-authored-by: florian <florian@gdevelop.io>

newIDE/app/.storybook/main.js

@@ -18,6 +18,5 @@ module.exports = {
       },
     },
     '@storybook/preset-create-react-app',
-    'storybook-addon-mock',
   ],
 };