ci: Update actions

- actions/checkout: 4 → 5
- cachix/install-nix-action: 27 → 31
  https://github.com/cachix/install-nix-action/releases/tag/v31
  https://github.com/cachix/install-nix-action/releases/tag/v30
  https://github.com/cachix/install-nix-action/releases/tag/v29
  https://github.com/cachix/install-nix-action/releases/tag/V28
- cachix/cachix-action: 15 → 16
  https://github.com/cachix/cachix-action/releases/tag/v16

Author: jtojnar

.github/workflows/main.yaml

@@ -38,13 +38,13 @@ jobs:
             storage: postgresql
     name: 'Check with PHP ${{ matrix.php }} and ${{ matrix.storage }} storage backend'
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
 
       - name: Install Nix
-        uses: cachix/install-nix-action@v27
+        uses: cachix/install-nix-action@v31
 
       - name: Set up Nix cache
-        uses: cachix/cachix-action@v15
+        uses: cachix/cachix-action@v16
         with:
           name: fossar
           authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
@@ -108,13 +108,13 @@ jobs:
     needs:
       - tests
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
 
       - name: Install Nix
         uses: cachix/install-nix-action@v27
 
       - name: Set up Nix cache
-        uses: cachix/cachix-action@v15
+        uses: cachix/cachix-action@v16
         with:
           name: fossar
           authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'