fix(security/unknown/x/k6): update go toolchain directive to v1.25.13 [security] (#242)

| datasource     | package | from    | to      |
| -------------- | ------- | ------- | ------- |
| golang-version | go      | 1.25.12 | 1.25.13 |

Signed-off-by: renovate-sh-app[bot] <219655108+renovate-sh-app[bot]@users.noreply.github.com>
Co-authored-by: renovate-sh-app[bot] <219655108+renovate-sh-app[bot]@users.noreply.github.com>

Author: renovate-sh-app[bot]

x/k6/go.mod

@@ -2,7 +2,7 @@ module github.com/grafana/pyroscope-go/x/k6
 
 go 1.25.0
 
-toolchain go1.25.12
+toolchain go1.25.13
 
 replace github.com/grafana/pyroscope-go => ../../