Wrong URL in preview links

[jbusecke]

This line in the preview comment workflow causes incorrect links to be posted:

✅ Deployment Preview URL: https://${{ github.repository_owner }}.github.io/${{ steps.repo-name.outputs.value }}/_preview/${{ inputs.pull_request_number }}/

See e.g in #50 this produces: https://leap-stc.github.io/leap-stc.github.io/_preview/53

whereas we should have this: https://leap-stc.github.io/_preview/53

Ill have to see how to generalize the cookbook action for this...for now Ill fix it in the hardcopy of the workflow here.