Remove braintree/braintree_php from magento/magento2-base

Nobody has claimed this yet.

### Summary (*)
`braintree/braintree_php` is required in `magento/magento2-base` when the only module that relies on that dependancy is `magento/module-braintree`, which also has `braintree/braintree_php` as a dependancy

I am not composer requiring `magento/product-community-edition` but instead `magento/magento2-base` with a subset of Magento modules, which I believe is a better practice than using composer's replace property to remove unused dependancies.

I don't want `braintree/braintree_php` to be installed as none of the modules I'm using make use of it.

### Examples (*)
N/A

### Proposed solution
I am suggesting removing `braintree/braintree_php` from `magento/magento2-base`, but **not** from `magento/product-community-edition` or `magento/product-enterprise-edition`

This should allow for `braintree/braintree_php` to only be installed via composer if `magento/module-braintree` is part of the resolved dependancies, and will keep `braintree/braintree_php` in the root composer.json if composer requiring `magento/product-*-edition` or cloning from git.

Other dependancies like `msp/recaptcha` have the ideal setup, where they get removed from `magento/magento2-base` when the composer.json package is created.

I don't believe I can create a pull request for this from the public GitHub repo.

Read the dependency declarations in magento/magento2-base and compare them with the root composer.json used by the product editions. Verify Composer resolution for a base installation without magento/module-braintree, while confirming the dependency remains available for the community and enterprise editions.

Written by the indexing model from the issue text.