enhance(ci): Workflow "Check Flake Groups" - Increasing Time to Complete

[Malix-Labs]

Subject

https://github.com/NixOS/nixos-search/blob/main/.github/workflows/check-flake-files.yml

Problem

The "Check Flake Groups" GitHub Action Workflow is taking an increasing amount of time to complete

Solution

Make it only check the patched lines rather than the whole https://github.com/NixOS/nixos-search/blob/main/flakes/manual.toml

References

• fix(deployment): flake import #1033 (concerns are somewhat related)
• https://github.com/tree-sitter/tree-sitter
• https://github.com/tree-sitter-grammars/tree-sitter-toml
• https://github.com/Wilfred/difftastic
• https://github.com/afnanenayet/diffsitter