fix(security/unknown/): update security go to v1.26.4 [security] (#2057)

| datasource     | package | from   | to     |
| -------------- | ------- | ------ | ------ |
| golang-version | go      | 1.26.3 | 1.26.4 |

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]

go.mod

@@ -2,7 +2,7 @@ module github.com/grafana/tanka
 
 go 1.26.1
 
-toolchain go1.26.3
+toolchain go1.26.4
 
 require (
 	github.com/Masterminds/semver v1.5.0