[INFRA] Use organization variables for runners

[csouchet]

See process-analytics/github-actions-playground#220 & process-analytics/bpmn-visualization-js#2465.

[tbouffard]

The variables (from repository and organization) are not available to GH workflow run when a Pull Request is created from fork repository. See https://github.com/orgs/community/discussions/44322.
We started working on the use of variables in January 2023, and the situation is the same on 2025-01-20.

So, we are closing the initiative