Bump install-nix-action

Author: lierdakil

.github/workflows/haskell.yml

@@ -7,7 +7,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v3
-    - uses: cachix/install-nix-action@v13
+    - uses: cachix/install-nix-action@v20
       with:
         nix_path: nixpkgs=channel:nixos-unstable
         extra_nix_config: |