build(deps): bump cachix/install-nix-action from 20 to 21 (#83)

Bumps [cachix/install-nix-action](https://github.com/cachix/install-nix-action) from 20 to 21.
- [Release notes](https://github.com/cachix/install-nix-action/releases)
- [Commits](cachix/install-nix-action@v20...v21)

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

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

.github/workflows/build.yml

@@ -27,7 +27,7 @@ jobs:
         uses: actions/checkout@v3
 
       - name: Install nix
-        uses: cachix/install-nix-action@v20
+        uses: cachix/install-nix-action@v21
         with:
           extra_nix_config: |
             access-tokens = github.com=${{ secrets.GITHUB_TOKEN }}

.github/workflows/pr.yml

@@ -49,7 +49,7 @@ jobs:
           fetch-depth: 0
 
       - name: Install nix
-        uses: cachix/install-nix-action@v20
+        uses: cachix/install-nix-action@v21
         with:
           extra_nix_config: |
             experimental-features = nix-command flakes

.github/workflows/update.yml

@@ -17,7 +17,7 @@ jobs:
           fetch-depth: 0
 
       - name: Install nix
-        uses: cachix/install-nix-action@v20
+        uses: cachix/install-nix-action@v21
         with:
           extra_nix_config: |
             experimental-features = nix-command flakes