Update dependency protobuf to v3.20.0

This MR contains the following updates:

Package	Type	Update	Change
protobuf	ironbank-pypi	minor	3.19.4 -> 3.20.0

---

Configuration

📅 Schedule: 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 this update again.

---

• If you want to rebase/retry this MR, click this checkbox.

---

This MR has been generated by Renovate Bot.