Deprecation Lines for BTPayPalNativeCheckout Module

[KunJeongPark]

Summary of changes

• Add deprecation message - @available(*, deprecated, message: "BraintreePayPalNativeCheckout Module is deprecated, use BraintreePayPal Module instead") for all public classes and enums for BraintreePayPalNativeCheckout module

Checklist

• [x] Added a changelog entry

Authors

List GitHub usernames for everyone who contributed to this pull request.

• @KunJeongPark