[Chore] Flakify xrefcheck

[krendelhoff2]

Description

For historical reasons some Serokell projects use niv to organize nix-related dependencies. However, the majority of other projects in our company use nix flakes to organize these dependencies.

Related issue(s)

Fixes #

:white_check_mark: Checklist for your Pull Request

Ideally a PR has all of the checkmarks set.

If something in this list is irrelevant to your PR, you should still set this checkmark indicating that you are sure it is dealt with (be that by irrelevance).

Related changes (conditional)

• Tests

  • [ ] If I added new functionality, I added tests covering it.
  • [ ] If I fixed a bug, I added a regression test to prevent the bug from silently reappearing again.

• Documentation

  • [ ] I checked whether I should update the docs and did so if necessary:
  • README
  • Haddock

• Public contracts

  • [ ] Any modifications of public contracts comply with the Evolution of Public Contracts policy.
  • [ ] I added an entry to the changelog if my changes are visible to the users and
  • [ ] provided a migration guide for breaking changes if possible

Stylistic guide (mandatory)

• [ ] My commits comply with the policy used in Serokell.
• [ ] My code complies with the style guide.

✓ Release Checklist

• [ ] I updated the version number in package.yaml.
• [ ] I updated the changelog and moved everything under the "Unreleased" section to a new section for this release version.
• [ ] (After merging) I edited the auto-release.
  • Change the tag and title using the format vX.Y.Z.
  • Write a summary of all user-facing changes.
  • Deselect the "This is a pre-release" checkbox at the bottom.
• [ ] (After merging) I updated xrefcheck-action.
• [ ] (After merging) I uploaded the package to hackage.

[rvem]

@krendelhoff2, is there anything that stops us from merging this PR?

[krendelhoff2]

@rvem should be ready to merge now