Don't add mikey179/vfsstream in CI - should be require-dev in composer.json

[GuySartorelli]

mikey179/vfsstream is being added for every module, regardless of if it is needed or not. We ideally shouldn't just add a package here that most modules don't need, as it means we could use some API from it in a non-assets module and the tests will pass even though it's not a dependency in that module.

The package is "Required for any module/recipe that runs silverstripe/assets unit tests" - so the composer.json for those modules/recipes should have it as a dev dependency.

What's more, it is being added with the constraint ^1.6.10 in CI which is necessary for PHP 8.1 but silverstripe/assets has it constrained too loosely as ^1.6.

composer require mikey179/vfsstream:^1.6.10 --dev --no-update

[emteknetnz]

This constraint is a require-dev of assets, though any meta packages like this recipe-core won't automatically install the require-dev of required packages, and assets is required by lots of meta packages

We should probably remove it from gha-ci and let builds fail on cron to see which meta-packages need it in require-dev