build(deps): bump cachix/install-nix-action from 19 to 20

Bumps [cachix/install-nix-action](https://github.com/cachix/install-nix-action) from 19 to 20.
- [Release notes](https://github.com/cachix/install-nix-action/releases)
- [Commits](https://github.com/cachix/install-nix-action/compare/v19...v20)

---
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>

.github/workflows/flake-updates-nixpkgs-update.yml

@@ -8,7 +8,7 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - name: Install Nix
-        uses: cachix/install-nix-action@v19
+        uses: cachix/install-nix-action@v20
         with:
           extra_nix_config: |
             experimental-features = nix-command flakes

.github/workflows/flake-updates.yml

@@ -10,7 +10,7 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - name: Install Nix
-        uses: cachix/install-nix-action@v19
+        uses: cachix/install-nix-action@v20
         with:
           extra_nix_config: |
             experimental-features = nix-command flakes

.github/workflows/terraform.yml

@@ -27,7 +27,7 @@ jobs:
           filters: |
             terraform:
               - 'terraform/**'
-      - uses: cachix/install-nix-action@v19
+      - uses: cachix/install-nix-action@v20
         if: steps.changes.outputs.terraform == 'true'
         with:
           extra_nix_config: |