[renovate] Update module github.com/prometheus/client_golang to v1.21.0

This MR contains the following updates:

Package	Type	Update	Change
github.com/prometheus/client_golang	require	minor	v1.20.5 -> v1.21.0

Important

Release Notes retrieval for this MR were skipped because no github.com credentials were available. If you are self-hosted, please see this instruction.

---

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 MR is behind base branch, 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, check this box

---

This MR has been generated by Renovate Bot.