[Braintree] Removed unnecessary unsets from models

[rogyar]

Description

This PR is a simple code cleanup. In the modified classes we don't need to unset the store_id from the array since it does not make sense. We don't pass the entire $data array like we do in \Magento\Braintree\Gateway\Http\Client\TransactionSale::process. Instead, we pass only particular array values. So, the unset operation for the array element is simply redundant.

Fixed Issues (if relevant)

N/A

Manual testing scenarios

N/A

[magento-engcom-team]

Hi @rogyar. Thank you for your contribution
Here is some useful tips how you can test your changes using Magento test environment.
Add the comment under your pull request to deploy test or vanilla Magento instance:

• @magento-engcom-team give me test instance - deploy test instance based on PR changes
• @magento-engcom-team give me {$VERSION} instance - deploy vanilla Magento instance

For more details, please, review the Magento Contributor Assistant documentation

[magento-engcom-team]

Hi @orlangur, thank you for the review.
ENGCOM-2658 has been created to process this Pull Request

[magento-engcom-team]

Hi @rogyar. Thank you for your contribution.
We will aim to release these changes as part of 2.3.0.
Please check the release notes for final confirmation.