chore(deps): 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] <support@github.com>

.github/workflows/test.yml

@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v4
-    - uses: cachix/install-nix-action@V28
+    - uses: cachix/install-nix-action@v29
     - run: nix flake lock
     - uses: stefanzweifel/git-auto-commit-action@v5
       with:
@@ -27,7 +27,7 @@ jobs:
       matrix: ${{ steps.set-matrix.outputs.matrix }}
     steps:
       - uses: actions/checkout@v4
-      - uses: cachix/install-nix-action@V28
+      - uses: cachix/install-nix-action@v29
       - id: set-matrix
         name: Generate Nix Matrix
         run: |
@@ -42,7 +42,7 @@ jobs:
     timeout-minutes: 30 # Safety net in case of hanging executable
     steps:
       - uses: actions/checkout@v4
-      - uses: cachix/install-nix-action@V28
+      - uses: cachix/install-nix-action@v29
       - uses: cachix/cachix-action@v15
         with:
           name: emacs-ci

.github/workflows/update-nixpkgs.yml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v4
-    - uses: cachix/install-nix-action@V28
+    - uses: cachix/install-nix-action@v29
       with:
         nix_path: nixpkgs=channel:nixos-unstable
     - name: Update snapshot commit

.github/workflows/update-snapshot.yml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v4
-    - uses: cachix/install-nix-action@V28
+    - uses: cachix/install-nix-action@v29
       with:
         nix_path: nixpkgs=channel:nixos-unstable
     - name: Update release snapshot commit