[Chore] Update "actions/checkout"

[Sereja313]

Problem: node16 is now deprecated and github-runner provided by nixpkgs no longer supports this runtime. However, "actions/checkout@v3" uses this runtime.

Solution: Update CI pipeline to use "actions/checkout@v4".

Description

Related issue(s)

Resolves #

Related changes (conditional)

• [ ] I checked whether I should update the README

• [ ] I checked whether native packaging works, i.e. native binary packages can be successfully built.

Stylistic guide (mandatory)

• [ ] My commits comply with the policy used in Serokell.

[Sereja313]

some of them use our runners, which causes scheduled jobs to fail

[rvem]

Hmm, I was grep'ing for checkout@v3 and as a result this repo got missed during my massive update :sweat_smile: