chore(deps): update actions/checkout action to v6

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
actions/checkout	action	major	v5 → v6

---

Release Notes

actions/checkout (actions/checkout)

v6

Compare Source

---

Configuration

📅 Schedule: 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 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 was generated by Mend Renovate. View the repository job log.

[yegor256]

@rultor please, try to merge, since 10 checks have passed

[rultor]

@rultor please, try to merge, since 10 checks have passed

@yegor256 OK, I'll try to merge now. You can check the progress of the merge here.

[rultor]

@rultor please, try to merge, since 10 checks have passed

@renovate[bot] @yegor256 Oops, I failed. You can see the full log here (spent 6s).

++ dirname ./run.sh
+ cd .
+ echo 1216
+ echo '2.0-SNAPSHOT BUILD'
2.0-SNAPSHOT BUILD
+ date
Fri Nov 21 16:51:05 UTC 2025
+ uptime
 16:51:05 up 1 min,  0 users,  load average: 0.59, 0.31, 0.12
+ cat
.rultor.yml in yegor256/objectionary-secrets doesn't allow objectionary/sodg.rs to use its assets (there are 36 friends), see http://doc.rultor.com/reference.html#assets
+ exit -1
'cid' file is absent, most probably the Docker container wasn't started correctly