How do I hide the shipping address the customer's receipt for a pickup order?

The order confirmation that is sent to the customer can be customized based on the shipping method selected. 

If you are offering in-store pickup for coreFORCE orders, you should already have a shipping method set up for pickup at your store location.

You can create an email order receipt that is specific to your store pickup location in Contacts > Email > Emails.  Find the email called RETAIL_STORE_ORDER_CONFIRMATION and click the Duplicate button to create a copy.  You can alter the text as needed to remove the customer's shipping address and show the address of the pickup location.

Then associate the new email with the correct shipping method in Orders > Settings > Shipping Methods.