chore(deps): update dependency go to v1.25.2 (#1649)

This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [go](https://go.dev/)
([source](https://redirect.github.com/golang/go)) | toolchain | patch |
`1.25.1` -> `1.25.2` |

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### Release Notes

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

###
[`v1.25.2`](https://redirect.github.com/golang/go/compare/go1.25.1...go1.25.2)

</details>

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Co-authored-by: Wenxin Du <117315983+duwenxin99@users.noreply.github.com>

go.mod

@@ -2,7 +2,7 @@ module github.com/googleapis/genai-toolbox
 
 go 1.24.7
 
-toolchain go1.25.1
+toolchain go1.25.2
 
 require (
 	cloud.google.com/go/alloydbconn v1.15.5