chore: Fix permissions for clear-pr-caches job

[KapJI]

DELETE /actions/caches endpoint requires action: write permission.

Failed job: https://github.com/twpayne/chezmoi/actions/runs/11769128068/job/32779753381

[twpayne]

Thanks!

[twpayne]

Hmm, it looks like there's still a problem here: https://github.com/twpayne/chezmoi/actions/runs/11778245494/job/32804280956

[KapJI]

After this change permissions changed from:

GITHUB_TOKEN Permissions
  Actions: read
  Attestations: read
  Checks: read
  Contents: read
  Deployments: read
  Discussions: read
  Issues: read
  Metadata: read
  Packages: read
  Pages: read
  PullRequests: read
  RepositoryProjects: read
  SecurityEvents: read
  Statuses: read

to:

GITHUB_TOKEN Permissions
  Actions: read
  Metadata: read

This is very likely caused by this setting in Settings->Actions->General. It looks like even explicit write permission in job config is not enough and you need to change that setting.

Another option is to remove this workflow and rely on default cache eviction behaviour, this shouldn't be too bad as well.

[KapJI]

It seems there is third option. lock-threads workflow shows that it's possible to set write permissions on workflow level.

Edit: #4081