Delete iPad text message app

This information describes the method by which Text Message Forwarding is enabled and managed on your devices. It follows, therefore, that you’ll be able selectively disable the features that you don’t require...

To enable, You must explicitly enable Text Message Forwarding for your iPad on your iPhone.

On your iPhone:

Settings > Messages > Text Message Forwarding - set to ON - and explicitly enable your iPad from the list of devices.

Also ensure that Messages in iCloud is enabled on both your iPhone and iPad:

Settings > [Your Name / AppleID] > Messages - set to ON

More information:

How to forward SMS/MMS text messages from your iPhone to your iPad, iPod touch or Mac - Apple Support

For iMessages, they are associated via your Apple ID, meaning you can’t. For SMS messages, go to the setting app (on the Phone) > Messages > Text Fowarding and turn it off for the IPad.