ci(github-action)!: Update cachix/install-nix-action action to v26

| datasource  | package                   | from | to  |
| ----------- | ------------------------- | ---- | --- |
| github-tags | cachix/install-nix-action | v23  | v26 |
| github-tags | cachix/install-nix-action | v25  | v26 |

.github/workflows/build-raspi4.yaml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4.1.1
-      - uses: cachix/install-nix-action@v23
+      - uses: cachix/install-nix-action@v26
         with:
           nix_path: nixpkgs=channel:nixos-23.05
           extra_nix_config: |

.github/workflows/diff-pr.yaml

@@ -50,7 +50,7 @@ jobs:
           fetch-depth: 0
 
       - name: Install nix
-        uses: cachix/install-nix-action@v25
+        uses: cachix/install-nix-action@v26
         with:
           extra_nix_config: |
             experimental-features = nix-command flakes

.github/workflows/nix-lint.yaml

@@ -14,7 +14,7 @@ jobs:
       uses: actions/checkout@v2
 
     - name: Install Nix
-      uses: cachix/install-nix-action@v23
+      uses: cachix/install-nix-action@v26
       with: 
         nix_path: nixpkgs=channel:nixos-unstable