Use env.GENERATED_BRANCH_NAME

.github/workflows/build-reference.yml

@@ -20,7 +20,7 @@ jobs:
       - name: Push generated antora files to the spring-generated-docs
         uses: JamesIves/github-pages-deploy-action@4.1.4
         with:
-          branch:  ${GENERATED_BRANCH_NAME} # The branch the action should deploy to.
+          branch:  ${{ env.GENERATED_BRANCH_NAME }} # The branch the action should deploy to.
           folder: "docs/build/generateAntora" # The folder the action should deploy.
           repository-name: "spring-io/spring-generated-docs"
           token: ${{ secrets.GH_ACTIONS_REPO_TOKEN }}