Bump cachix/install-nix-action from V27 to 29 (#4411)

Bumps [cachix/install-nix-action](https://github.com/cachix/install-nix-action) from V27 to 29. This release includes the previously tagged commit.
- [Release notes](https://github.com/cachix/install-nix-action/releases)
- [Commits](cachix/install-nix-action@V27...v29)

---
updated-dependencies:
- dependency-name: cachix/install-nix-action
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/nix.yml

@@ -49,7 +49,7 @@ jobs:
     steps:
     - uses: actions/checkout@v3
 
-    - uses: cachix/install-nix-action@V27
+    - uses: cachix/install-nix-action@v29
       with:
         extra_nix_config: |
           experimental-features = nix-command flakes