deps: update dependency go to v1.23.6 (#259)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [go](https://go.dev/)
([source](https://redirect.github.com/golang/go)) | toolchain | patch |
`1.23.5` -> `1.23.6` |

---

### Release Notes

<details>
<summary>golang/go (go)</summary>

###
[`v1.23.6`](https://redirect.github.com/golang/go/compare/go1.23.5...go1.23.6)

</details>

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go.mod

@@ -2,7 +2,7 @@ module github.com/hetznercloud/packer-plugin-hcloud
 
 go 1.21.0
 
-toolchain go1.23.5
+toolchain go1.23.6
 
 require (
 	github.com/hashicorp/hcl/v2 v2.23.0