PR: fixing Rekku private key

.github/workflows/pr_from_upstream.yml

@@ -19,21 +19,12 @@ jobs:
           git checkout "${{ github.ref_name }}"
           git branch --set-upstream-to=upstream/${{ github.ref_name }} ${{ github.ref_name }}
 
-      - name: Debug Private Key
-        run: |
-          echo "Testing access to REKKU_PRIVATE_KEY"
-          if [ -z "${{ secrets.REKKU_PRIVATE_KEY }}" ]; then
-            echo "Error: secret REKKU_PRIVATE_KEY not available."
-            exit 1
-          fi
-          echo "Secret REKKU_PRIVATE_KEY available."
-
       - name: Generate a token for Rekku
         id: generate-rekku-token
         uses: actions/create-github-app-token@v1
         with:
           app-id: ${{ vars.REKKU_APP_ID }}
-          private-key: ${{ secrets.REKKU_PRIVATE_KEY }}
+          private-key: ${{ inputs.REKKU_PRIVATE_KEY }}
           owner: "RetroDECK"
 
       - name: Configuring Git