Update cachix/install-nix-action action to v31

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
cachix/install-nix-action	action	major	v30 -> v31

---

Release Notes

cachix/install-nix-action (cachix/install-nix-action)

v31

Compare Source

Starting with v31, this action will use semantic versioning for releases.
Major tags, like v31, will be bumped to point to the latest minor/patch release.
This is in line with how most GitHub actions manage releases.

What's Changed

• nix: 2.26.3 -> 2.28.2 by @​Mic92 in https://github.com/cachix/install-nix-action/pull/232
• nix: 2.24.9 -> 2.25.2 by @​Mic92 in https://github.com/cachix/install-nix-action/pull/218
• ci: fix latest installer tests by @​sandydoo in https://github.com/cachix/install-nix-action/pull/220
• ci: add ubuntu-24.04-arm to matrix by @​msgilligan in https://github.com/cachix/install-nix-action/pull/221
• nix: 2.25.2 -> 2.26.2 by @​Mic92 in https://github.com/cachix/install-nix-action/pull/226
• nix: 2.26.2 -> 2.26.3 by @​sandydoo in https://github.com/cachix/install-nix-action/pull/228
• feat: Pin actions to hashes by @​l0b0 in https://github.com/cachix/install-nix-action/pull/201
• chore(deps): bump actions/checkout from 4.1.1 to 4.2.2 by @​dependabot in https://github.com/cachix/install-nix-action/pull/234
• docs: document how to provide AWS credentials to the nix-daemon by @​sandydoo in https://github.com/cachix/install-nix-action/pull/235
• nix: 2.28.2 -> 2.28.3 by @​Mic92 in https://github.com/cachix/install-nix-action/pull/236

New Contributors

• @​msgilligan made their first contribution in https://github.com/cachix/install-nix-action/pull/221

Full Changelog: cachix/install-nix-action@v30...v31

---

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.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}