[ENH] CI: Cancel previous workflows on the same pull request

[Moritz-Alexander-Kern]

This pull request introduces an enhancement to our GitHub Actions workflow.

The added lines in the GitHub Actions YAML file enable the cancellation of previous workflows associated with the same pull request.

# Cancel previous workflows on the same pull request
concurrency:
  group: ${{ github.workflow }}-${{ github.ref }}
  cancel-in-progress: true

With these changes, we ensure that only the latest workflow for a given pull request will be executed, enhancing efficiency. This adjustment is particularly beneficial in scenarios where multiple workflows for the same pull request may overlap.

[coveralls]

coverage: 87.902% (-0.3%) from 88.235%
when pulling 2d72690 on INM-6:enh/github_CI
into a93bac0 on NeuralEnsemble:master.

[Moritz-Alexander-Kern]

Test: see test run #660 and #661.

Run #660 was canceled when #661 was triggered.

[Moritz-Alexander-Kern]

build wheels

[Moritz-Alexander-Kern]

Unfortunately not compatible with coveralls.io. Re-open if resolved.