ci: cancel runs on new commits

[YYYasin19]

Our CI currently let's runners run on old commits even though a newer one arrived. This can be solved pretty easy by adding the following concurrency group to the ci.yaml file:

name: Workflow X

on: # ...

concurrency:
  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
  cancel-in-progress: true

jobs: # ...

This can save resources (and make this faster, if you have a limited amount of runners)