chore: pin the nix version to avoid some issues

[somebodyLi]

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[what-the-diff]

PR Summary

• Updated Nix installation script in .github/workflows/build-classic.yml
  The Nix installation command was updated to point to a newer version for improved functionality and possible bug fixes.

• Improved Nix installation script in .github/workflows/build-mini.yml
  A similar change has been made here to keep the versions consistent across workflows, ensuring stable performance.

• Modified Nix installation command in .github/workflows/build-touch.yml
  This update ensures that all workflow files are using the same, latest version of the Nix installation script for consistency and reliability.