Update mitre/heimdall2 Docker tag to v2.9.3

This MR contains the following updates:

Package	Type	Update	Change
mitre/heimdall2		patch	2.9.2 -> 2.9.3
mitre/heimdall2	ironbank-docker	patch	2.9.2 -> 2.9.3
mitre/heimdall2	stage	patch	2.9.2 -> 2.9.3

---

Configuration

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

🚦 Automerge: Enabled.

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

🔕 Ignore: Close this MR and you won't be reminded about these updates again.

---

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

---

This MR has been generated by Renovate Bot.