Bump cachix/install-nix-action from 18 to 20

Author: rszamszur

.github/workflows/main.yml

@@ -47,7 +47,7 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - name: Install Nix ❄️
-        uses: cachix/install-nix-action@v18
+        uses: cachix/install-nix-action@v20
         with:
           nix_path: ${{ env.NIX_CHANNEL }}
           install_url: ${{ env.NIX_INSTALL_URL }}

template/{% if github_actions %}.github{% endif %}/workflows/{% if nix %}nix.yml{% endif %}.jinja

@@ -34,7 +34,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: cachix/install-nix-action@v18
+      - uses: cachix/install-nix-action@v20
         with:
           nix_path: ${{ env.NIX_CHANNEL }}
           install_url: ${{ env.NIX_INSTALL_URL }}
@@ -67,7 +67,7 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - name: Install Nix ❄️
-        uses: cachix/install-nix-action@v18
+        uses: cachix/install-nix-action@v20
         with:
           extra_nix_config: "system-features = nixos-test benchmark big-parallel kvm"
           nix_path: ${{ env.NIX_CHANNEL }}