fix: use correct heroku token

Author: BolajiOlajide

.github/workflows/stage.yml

@@ -9,7 +9,7 @@ jobs:
     if: github.event_name == 'push' && github.ref == 'refs/heads/master'
 
     env:
-      HEROKU_API_TOKEN: ${{ secrets.HEROKU_API_TOKEN }}
+      HEROKU_API_KEY: ${{ secrets.HEROKU_API_TOKEN }}
 
     runs-on: ubuntu-latest