Bump cachix/install-nix-action from 30 to 31 (#261)

Author: 4ever2

.github/workflows/nix-action-8.20.yml

@@ -33,7 +33,7 @@ jobs:
         fetch-depth: 0
         ref: ${{ env.tested_commit }}
     - name: Cachix install
-      uses: cachix/install-nix-action@v30
+      uses: cachix/install-nix-action@v31
       with:
         nix_path: nixpkgs=channel:nixpkgs-unstable
     - name: Cachix setup au-cobra
@@ -116,7 +116,7 @@ jobs:
         fetch-depth: 0
         ref: ${{ env.tested_commit }}
     - name: Cachix install
-      uses: cachix/install-nix-action@v30
+      uses: cachix/install-nix-action@v31
       with:
         nix_path: nixpkgs=channel:nixpkgs-unstable
     - name: Cachix setup au-cobra
@@ -178,7 +178,7 @@ jobs:
         fetch-depth: 0
         ref: ${{ env.tested_commit }}
     - name: Cachix install
-      uses: cachix/install-nix-action@v30
+      uses: cachix/install-nix-action@v31
       with:
         nix_path: nixpkgs=channel:nixpkgs-unstable
     - name: Cachix setup au-cobra
@@ -249,7 +249,7 @@ jobs:
         fetch-depth: 0
         ref: ${{ env.tested_commit }}
     - name: Cachix install
-      uses: cachix/install-nix-action@v30
+      uses: cachix/install-nix-action@v31
       with:
         nix_path: nixpkgs=channel:nixpkgs-unstable
     - name: Cachix setup au-cobra
@@ -310,7 +310,7 @@ jobs:
         fetch-depth: 0
         ref: ${{ env.tested_commit }}
     - name: Cachix install
-      uses: cachix/install-nix-action@v30
+      uses: cachix/install-nix-action@v31
       with:
         nix_path: nixpkgs=channel:nixpkgs-unstable
     - name: Cachix setup au-cobra
@@ -364,7 +364,7 @@ jobs:
         fetch-depth: 0
         ref: ${{ env.tested_commit }}
     - name: Cachix install
-      uses: cachix/install-nix-action@v30
+      uses: cachix/install-nix-action@v31
       with:
         nix_path: nixpkgs=channel:nixpkgs-unstable
     - name: Cachix setup au-cobra
@@ -442,7 +442,7 @@ jobs:
         fetch-depth: 0
         ref: ${{ env.tested_commit }}
     - name: Cachix install
-      uses: cachix/install-nix-action@v30
+      uses: cachix/install-nix-action@v31
       with:
         nix_path: nixpkgs=channel:nixpkgs-unstable
     - name: Cachix setup au-cobra