RenovateBot: Update docker Docker tag to v20.10.20

This MR contains the following updates:

Package	Type	Update	Change
docker	service-image	patch	20.10.19-dind -> 20.10.20-dind
docker	image	patch	20.10.19 -> 20.10.20

---

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, click this checkbox.

---

This MR has been generated by Renovate Bot.