Update docker/build-push-action action to v6

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
docker/build-push-action	action	major	v5 -> v6

---

Release Notes

docker/build-push-action (docker/build-push-action)

v6

Compare Source

---

Configuration

📅 Schedule: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined).

🚦 Automerge: Disabled by config. Please merge this manually once you are satisfied.

♻ Rebasing: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 Ignore: Close this PR and you won't be reminded about this update again.

---

• If you want to rebase/retry this PR, check this box

---

This PR has been generated by Mend Renovate. View repository job log here.

[github-actions]

The Docker Image can now be found here: ghcr.io/zoeyvid/curl-quic:pr-92