GitHub Script action not pinned to a full-length commit SHA

The `accessibility-scanner` workflow uses `actions/github-script@v8` without pinning it to a specific commit SHA. This violates security best practices and causes the pipeline to fail when the **Require actions to be pinned to a full-length commit SHA** setting is enabled.

#### **Steps to Reproduce**
1. Enable **Require actions to be pinned to a full-length commit SHA** in the repository settings.
2. Run the `accessibility-scanner` workflow.
3. Observe the failure caused by the unpinned `actions/github-script` action.

#### **Expected Behavior**
The workflow should run successfully with all actions pinned to full-length commit SHAs.

#### **Actual Behavior**
The workflow fails because `actions/github-script@v8` is not pinned to a commit SHA.

https://github.com/github/accessibility-scanner/blob/db51bb5d470a862cc027836ee1583ab9d5ae5b16/action.yml#L137

Commencez par action.yml à la ligne 137, référencé dans l'issue, et examinez l'utilisation de actions/github-script dans le workflow accessibility-scanner. Mettez à jour la référence de l'action vers un SHA de commit complet, puis vérifiez que le workflow respecte l'exigence de pinning du dépôt et s'exécute correctement.

Rédigé par le modèle d'indexation à partir du texte de l'issue.