Bump install-nix-action (#625)

Author: michaelpj

.github/workflows/format.yaml

@@ -12,7 +12,7 @@ jobs:
 
     steps:
       - uses: actions/checkout@v3
-      - uses: cachix/install-nix-action@v22
+      - uses: cachix/install-nix-action@v31
         with:
           nix_path: nixpkgs=channel:nixos-unstable
       - run: nix-shell --run "fourmolu -m check ."

.github/workflows/nix.yaml

@@ -17,7 +17,7 @@ jobs:
 
     steps:
       - uses: actions/checkout@v3
-      - uses: cachix/install-nix-action@v22
+      - uses: cachix/install-nix-action@v31
         with:
           nix_path: nixpkgs=channel:nixos-unstable
       - run: nix-shell --run "cabal update && cabal build all"