chore(deps): update cachix/install-nix-action action to v29

Author: renovate[bot]

.github/workflows/ci.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v4
-      - uses: cachix/install-nix-action@v27
+      - uses: cachix/install-nix-action@v29
         with:
           github_access_token: ${{ secrets.GITHUB_TOKEN }}
       - name: Run checks