Bump cachix/install-nix-action from V28 to 29

Bumps [cachix/install-nix-action](https://github.com/cachix/install-nix-action) from V28 to 29. This release includes the previously tagged commit.
- [Release notes](https://github.com/cachix/install-nix-action/releases)
- [Commits](cachix/install-nix-action@V28...v29)

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

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -16,7 +16,7 @@ jobs:
     runs-on: "${{ matrix.os }}"
     steps:
       - uses: actions/checkout@v4
-      - uses: cachix/install-nix-action@V28
+      - uses: cachix/install-nix-action@v29
       - uses: cachix/cachix-action@v15
         with:
           name: dschrempf-nix-script
@@ -31,7 +31,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - uses: cachix/install-nix-action@V28
+      - uses: cachix/install-nix-action@v29
       - uses: cachix/cachix-action@v15
         with:
           name: nix-script

.github/workflows/nix.yml

@@ -13,7 +13,7 @@ jobs:
       - uses: actions/checkout@v4
         with:
           ref: main
-      - uses: cachix/install-nix-action@V28
+      - uses: cachix/install-nix-action@v29
       - run: nix flake update
       - name: Create PR
         env: