Fix/phone validation

[lauramelos]

All Submissions:

• Does your code follow the Extendables standards?
• Have you written new tests for your changes, as applicable?
• Have you successfully run tests with your changes locally?

Changes proposed in this Pull Request:

Closes #288

How to test the changes in this Pull Request:

1. Checkout block should be used instead of the shortcode
2. Go to site, add shippable product and go to checkout
3. Select local pickup and fill the checkout form
4. Select Amazon Pay and place order (no validation message)

Other information:

• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Changelog entry

Fix Billing phone number validation on local pickup