Outdated URL in phrase braintree_api_keys_explain

[soloarquitectura]

Affected version

2.2.13

Outdated: https://articles.braintreepayments....al-credentials-in-the-braintree-control-panel (although it is true that it has redirection).

New URL is: https://developer.paypal.com/braintree/articles/guides/payment-methods/paypal/setup-guide