Remove default entity form display install config

Problem/Motivation

The default entity form display dc_ajax_add_cart is being created inside dc_ajax_add_cart_install(). And there is also an install config for the default entity form display. The latter should be removed. Otherwise it would be redundant code.

Proposed resolution

Remove the install config of default entity form display dc_ajax_add_cart.

Remaining tasks

N/A

User interface changes

N/A

API changes

N/A

Data model changes

N/A