fix: phone number on ShippingContact is a string

[huextrat]

Summary

phoneNumber type on ShippingContact for ApplePay is a string not a number

Motivation

Native mappers mapFromShippingContact give the phone number as a string but TS type is a number which is wrong.

Testing

• I tested this manually
• I added automated tests

Documentation

Select one:

• I have added relevant documentation for my changes.
• This PR does not result in any developer-facing changes.

[charliecruzan-stripe]

thanks for this!