task: op-geth deprecation notice still says the switch is ahead

### What needs to be done?

`operate/notices/op-geth-deprecation.mdx` is written throughout as if the switch to `op-reth` is still ahead. It isn't. The page's own dates are:

- Celo Sepolia: June 24, 2026
- Mainnet: July 22, 2026

Both are past. Lines that no longer hold:

- L6: "outlines the deprecation ... and the transition to `op-reth`"
- L8: "Celo **is switching** its execution client ... All node operators **must migrate** ... **by the switch date**"
- L17: "Celo **will also** discontinue support for `op-geth` and adopt `op-reth`"
- L19: "`op-geth`: Supported **only until** the switch date"
- L25: "Node operators **must complete** migration ... by the switch date"
- L38: "validating your integrations against `op-reth` on Celo Sepolia, **which switches first**"

Two other pages carry the same future framing in their execution-client callouts:

- `operate/operators/run-node.mdx:12` — "the execution client Celo **is adopting** as its primary client"
- `operate/operators/archive-node.mdx:16` — "`op-geth` **is supported until** your network's switch date"

This is a rewrite, not a verb swap. A notice whose event has happened either states what happened and what an operator still running `op-geth` should do now, or moves to `operate/notices/archive/` like the other completed notices. Worth deciding which.

### Definition of done

- [ ] `operate/notices/op-geth-deprecation.mdx` describes a completed switch, or is archived with a redirect
- [ ] `run-node.mdx:12` and `archive-node.mdx:16` match
- [ ] `mint broken-links` green

### Priority

medium

### Size

S — hours

Refs #2309. The tense on `operate/index.mdx` and `operate/operators/overview.mdx` was already fixed there.

Read operate/notices/op-geth-deprecation.mdx and compare completed notices under operate/notices/archive/ to decide whether to rewrite the notice or archive it with a redirect. Update the execution-client callouts in operate/operators/run-node.mdx and operate/operators/archive-node.mdx, then run mint broken-links; done means all three pages reflect the completed switch and the check is green.

Written by the indexing model from the issue text.