Update module github.com/caddyserver/certmagic to v0.21.7 (forgejo) (#6604)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [github.com/caddyserver/certmagic](https://github.com/caddyserver/certmagic) | require | patch | `v0.21.6` -> `v0.21.7` |

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### Release Notes

<details>
<summary>caddyserver/certmagic (github.com/caddyserver/certmagic)</summary>

### [`v0.21.7`](https://github.com/caddyserver/certmagic/compare/v0.21.6...v0.21.7)

[Compare Source](https://github.com/caddyserver/certmagic/compare/v0.21.6...v0.21.7)

</details>

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Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/6604
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