chore(deps): update golang docker tag to v1.26

This MR contains the following updates:

Package	Type	Update	Change
golang	stage	minor	1.25 → 1.26

---

Configuration

📅 Schedule: (in timezone Europe/Zurich)

• Branch creation
  • At any time (no schedule defined)
• Automerge
  • At any time (no schedule defined)

🚦 Automerge: Disabled by config. Please merge this manually once you are satisfied.

♻️ Rebasing: Whenever MR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 Ignore: Close this MR and you won't be reminded about this update again.

---

• If you want to rebase/retry this MR, check this box

---

This MR has been generated by Mend Renovate.