This is a WooCommerce feature. You can just change this in the WooCommerce shipping options.
WooCommerce–> Settings –> Shipping–> Shipping Option –> (select) Force shipping to the customer billing address.
Disable “Ship to different address”

Once done, the box “Ship to a different address” will be hidden on the checkout page
Uncheck “Ship to different address”
Out of the box, if you want to uncheck the box by default, please go to WooCommerce–> Settings –> Shipping–> Shipping Option –> (select) Default to customer billing address.

Once done, “Ship to a different address” will not checked by default.
Hope that helps!