Drop Composer 1 from workflows

[jooname]

Composer 1 support was shut down in September 2025 and it's not possible to use it anymore. This results in the workflows for this package to also fail:

Run composer require --dev composer/composer:1.10.27 --no-update
Warning from [https://repo.packagist.org:](https://repo.packagist.org/) Support for Composer 1 has been shutdown on September 1st 2025. You should upgrade to Composer 2. See https://blog.packagist.com/shutting-down-packagist-org-support-for-composer-1-x/

                                                                                                                                                                                  
  [InvalidArgumentException]                                                                                                                                                      
  Could not find a version of package composer/composer matching your minimum-stability (stable). Require it with an explicit version constraint allowing its desired stability.

At the very least the workflows in the package must be updated to not use Composer 1, so that we can continue using the workflows for further development. Dropping the compatibility entirely from the package is optional since there can be still projects out there using Private Packagist where extended support is still available.