How to remove the hidden apps folder on iPad Pro?

it's a part of the operating system

you can read about it here

Lock or hide an app on iPhone - Apple Support

if you wish apple to let you remove / deactivate the feature on your device then

you can suggest to them that they make this feature available using their feedback channels

Product Feedback - Apple

The Hidden Apps folder that you see within the App Library cannot be deleted. While it cannot be removed from the App Library, you don't have to use it.

Apple invite submission of comments and feature requests via its Product Feedback portal. If you would like to see a specific feature or functionality in a future version of iPadOS, this would be the most appropriate channel through which to make a request:

Feedback - iPad - Apple