Update the shop.tax_shipping type

[lizkenyon]

Description

Fixes #1271

The tax_shipping field will be null on newly created stores. true when enabled and false when subsequently disabled.

How has this been tested?

• Tested in a development app

Checklist:

• [x] My commit message follow the pattern described in here
• [x] I have performed a self-review of my own code.
• [x] I have added a changelog line.