Action fails when running for PR from a fork

[Luthaf]

See for example metatensor/metatensor#820

Running with GHA debug logging gives me:

##[debug]Evaluating condition for step: 'Comment with download link'
##[debug]Evaluating: success()
##[debug]Evaluating success:
##[debug]=> true
##[debug]Result: true
##[debug]Starting: Comment with download link
##[debug]Loading inputs
##[debug]Evaluating: github.token
##[debug]Evaluating Index:
##[debug]..Evaluating github:
##[debug]..=> Object
##[debug]..Evaluating String:
##[debug]..=> 'token'
##[debug]=> '***'
##[debug]Result: '***'
##[debug]Evaluating: github.repository
##[debug]Evaluating Index:
##[debug]..Evaluating github:
##[debug]..=> Object
##[debug]..Evaluating String:
##[debug]..=> 'repository'
##[debug]=> 'metatensor/metatensor'
##[debug]Result: 'metatensor/metatensor'
##[debug]Evaluating: github.run_id
##[debug]Evaluating Index:
##[debug]..Evaluating github:
##[debug]..=> Object
##[debug]..Evaluating String:
##[debug]..=> 'run_id'
##[debug]=> '12866182743'
##[debug]Result: '12866182743'
##[debug]Loading env

[PR TEXT …]

##[debug]
##[debug]<!-- download-section Documentation docs start -->
##[debug][📚 Download documentation for this pull-request](https://nightly.link/metatensor/metatensor/actions/artifacts/2455811253.zip)
##[debug]
##[debug]<!-- download-section Documentation docs end -->
Error: Resource not accessible by integration
##[debug]Node Action run completed with exit code 1
##[debug]Finishing: Comment with download link

[Luthaf]

Maybe relevant as a way to skip running this from a fork: peaceiris/actions-gh-pages#153 (comment)

[PicoCentauri]

Good catch. I will take a look!