ci: another attempt to fix documentation CI (#1231)

.github/workflows/pull_request_secure.yml

@@ -266,7 +266,7 @@ jobs:
     name: Build Documentation
     env:
       BRANCH_NAME: ${{ github.head_ref || github.ref_name }}
-      HEAD_OWNER: ${{ github.event.pull_request.head.repo.owner.login }}
+      GURL: "https://github.com/${{ github.event.pull_request.head.repo.owner.login || 'TimefoldAI' }}/timefold-solver"
     steps:
       - name: Install yq
         run: |
@@ -291,9 +291,6 @@ jobs:
         env:
           GIT_CREDENTIALS: ${{ secrets.GIT_CREDENTIALS }}
         run: |
-          export GURL="https://github.com/$(HEAD_OWNER)/timefold-solver"
-          echo $GURL
-          echo $BRANCH_NAME
           yq -i e 'del(.content.sources)' apps/docs/antora-playbook.yml
           yq -i e 'del(.site.keys)' apps/docs/antora-playbook.yml
           yq -i e '.content.sources += [{"url": env(GURL), "branches": env(BRANCH_NAME), "start_path": "docs/src"}]' apps/docs/antora-playbook.yml