[2.2.0-RC2.0] composer/composer dependency in generated composer.json still at stability @alpha

[hostep]

Preconditions

1. PHP 7.0.22
2. Have composer installed

Steps to reproduce

1. Execute:

$ mkdir mage22test
$ cd mage22test
$ composer create-project --no-install --repository-url=https://repo.magento.com/ --stability=RC magento/project-community-edition .
$ cat composer.json | grep composer/composer

Expected result

1. No requirement on composer/composer and especially not with the @alpha constraint

Actual result

1. Output of grep: "composer/composer": "@alpha"

Discussion

It was decided to stabilize the composer dependency over here: #4359

So there should be no @alpha constraint in the resulting composer.json
The requirement can probably be removed entirely since it is already a dependency of the packages: magento/composer and magento/framework and magento/magento2-base and magento/product-community-edition

(magento/magento-composer-installer also still has a dependency on: "composer/composer": "*@dev", but that's probably less important to fix)

[fooman]

Can confirm this - resulting composer.json:

"require": {
    "magento/product-community-edition": "2.2.0-rc20",
    "composer/composer": "@alpha"
}

[korostii]

By the way, composer is also still at @alpha if you download the prepackaged archive from https://magento.com/tech-resources/download