Fix name mismatch on 14 - Build Pipeline.md

[Claudiferock]

Fix name mismatch

The current code sample on the readme documentation gives a different secret name ${{ secrets.BUCKET_ID }} to the one used during the workshop ${{ secrets.BUCKET_NAME }}

I referred to the readme when creating the secrets on GitHub and kept failing my tests, until I realized I used the wrong name 🙃 Hopefully this prevents others from having the same issue.