If we take the below facts:
 - The country select is set as disabled
   when Shipping is set to "Ship to the same address"
 - The disable property of select inputs is
   removed when shipping is set to
   `create a new address`:
   In `website_sale.js`:
   ```
   $selects.attr("disabled", value <= 0 ? null : "disabled" ).prop("disabled", value <= 0 ? null : "disabled" );
   ```

We can safely assume that the select input "State / Province" was supposed
to be set as `disabled` in the first place, not as `readonly`

Before this revision, State / Provice was greyed when choosing
"Create a new address" for shipping, and selecting the United States
(but the select input was still usable, though, it was just greyed)

opw-675739