chore(deps): update golang:1.25.3 docker digest to 6bac879 (#1398)

Co-authored-by: elastic-renovate-prod[bot] <174716857+elastic-renovate-prod[bot]@users.noreply.github.com>

Author: elastic-renovate-prod[bot]

.buildkite/release.yml

@@ -1,7 +1,7 @@
 steps:
   - label: Release
     agents:
-      image: "golang:1.25.3@sha256:dd08f769578a5f51a22bf6a81109288e23cfe2211f051a5c29bd1c05ad3db52a"
+      image: "golang:1.25.3@sha256:6bac879c5b77e0fc9c556a5ed8920e89dab1709bd510a854903509c828f67f96"
       cpu: "16"
       memory: "24G"
       ephemeralStorage: "20G"