Bump cachix/install-nix-action from 17 to 18 (#2)

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](https://github.com/cachix/install-nix-action/compare/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/dotnet.yaml

@@ -40,7 +40,7 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v3
       - name: Install Nix
-        uses: cachix/install-nix-action@v17
+        uses: cachix/install-nix-action@v18
         with:
           extra_nix_config: |
             access-tokens = github.com=${{ secrets.GITHUB_TOKEN }}
@@ -53,7 +53,7 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v3
       - name: Install Nix
-        uses: cachix/install-nix-action@v17
+        uses: cachix/install-nix-action@v18
         with:
           extra_nix_config: |
             access-tokens = github.com=${{ secrets.GITHUB_TOKEN }}
@@ -66,7 +66,7 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v3
       - name: Install Nix
-        uses: cachix/install-nix-action@v17
+        uses: cachix/install-nix-action@v18
         with:
           extra_nix_config: |
             access-tokens = github.com=${{ secrets.GITHUB_TOKEN }}
@@ -79,7 +79,7 @@ jobs:
     steps:
       - uses: actions/checkout@master
       - name: Install Nix
-        uses: cachix/install-nix-action@v17
+        uses: cachix/install-nix-action@v18
         with:
           extra_nix_config: |
             access-tokens = github.com=${{ secrets.GITHUB_TOKEN }}