Bump cachix/install-nix-action from 17 to 18 (#3292)

Bumps [cachix/install-nix-action](https://github.com/cachix/install-nix-action) from 17 to 18.
- [Release notes](https://github.com/cachix/install-nix-action/releases)
- [Commits](cachix/install-nix-action@v17...v18)

---
updated-dependencies:
- dependency-name: cachix/install-nix-action
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

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

.github/workflows/nix.yml

@@ -55,7 +55,7 @@ jobs:
     steps:
     - uses: actions/checkout@v3
 
-    - uses: cachix/install-nix-action@v17
+    - uses: cachix/install-nix-action@v18
       with:
         install_url: https://nixos-nix-install-tests.cachix.org/serve/i6laym9jw3wg9mw6ncyrk6gjx4l34vvx/install
         install_options: '--tarball-url-prefix https://nixos-nix-install-tests.cachix.org/serve'
@@ -89,7 +89,7 @@ jobs:
     steps:
     - uses: actions/checkout@v3
 
-    - uses: cachix/install-nix-action@v17
+    - uses: cachix/install-nix-action@v18
       with:
         install_url: https://nixos-nix-install-tests.cachix.org/serve/i6laym9jw3wg9mw6ncyrk6gjx4l34vvx/install
         install_options: '--tarball-url-prefix https://nixos-nix-install-tests.cachix.org/serve'