build(deps): update hk to v1.15.6

This MR contains the following updates:

| Package | Update | Change |
|---|---|---|
| [hk](https://github.com/jdx/hk) | patch | `1.15.5` -> `1.15.6` |

MR created with the help of [el-capitano/tools/renovate-bot](https://gitlab.com/el-capitano/tools/renovate-bot).

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### Release Notes

<details>
<summary>jdx/hk (hk)</summary>

### [`v1.15.6`](https://github.com/jdx/hk/blob/HEAD/CHANGELOG.md#1156---2025-09-25)

[Compare Source](jdx/hk@v1.15.5...v1.15.6)

##### 🐛 Bug Fixes

- issue with generated file staging by [@&#8203;jdx](https://github.com/jdx) in [#&#8203;307](jdx/hk#307)

</details>

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Author: ECG Bot

chezmoi/dot_config/mise/config.toml

@@ -5,7 +5,7 @@ fd = "10.2.0"
 glab = "1.67.0"
 go = "1.25.1"
 hcloud = "1.51.0"
-hk = "1.15.5"
+hk = "1.15.6"
 node = "24.8.0"
 pkl = "0.29.1"
 python = "3.13.7"