tools: use ad-hoc flag to lint Nix files

Here's what `treefmt --help` documents:

`--ci`: Runs `treefmt` in a CI mode, enabling `--no-cache`,
        `--fail-on-change` and adjusting some other settings best suited
        to a CI use case.

PR-URL: #61405
Reviewed-By: Daijiro Wachi <[email protected]>
Reviewed-By: Luigi Pinca <[email protected]>
Reviewed-By: Colin Ihrig <[email protected]>

Author: aduh95

.github/workflows/linters.yml

@@ -153,7 +153,7 @@ jobs:
       - name: Lint Nix files
         run: |
           nix-shell -I nixpkgs=./tools/nix/pkgs.nix -p 'nixfmt-tree' --run '
-            treefmt --quiet --fail-on-change
+            treefmt --quiet --ci
           ' || git --no-pager diff --exit-code
 
   lint-py: