Update actions/checkout action to v6

[simplificator-renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
actions/checkout	action	major	v4 -> v6

---

Release Notes

actions/checkout (actions/checkout)

v6

Compare Source

• Persist creds to a separate file by @​ericsciple in https://github.com/actions/checkout/pull/2286
• Update README to include Node.js 24 support details and requirements by @​salmanmkc in https://github.com/actions/checkout/pull/2248

v5

Compare Source

• Port v6 cleanup to v5 by @​ericsciple in https://github.com/actions/checkout/pull/2301

---

Configuration

📅 Schedule: Branch creation - "before 8am on monday" (UTC), Automerge - At any time (no schedule defined).

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

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

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

---

• [ ] If you want to rebase/retry this PR, check this box

---

This PR has been generated by Renovate Bot.