Update actions/checkout to v4 in the template

[simu]

Checklist

• The PR has a meaningful title. It will be used to auto generate the
  changelog.
  The PR has a meaningful description that sums up the change. It will be
  linked in the changelog.
• PR contains a single logical change (to build a better changelog).
• Categorize the PR by adding one of the labels:
  bug, enhancement, documentation, change, breaking, dependency
  as they show up in the changelog.