Bump DeterminateSystems/magic-nix-cache-action from 2 to 4 (#631)

Bumps [DeterminateSystems/magic-nix-cache-action](https://github.com/determinatesystems/magic-nix-cache-action) from 2 to 4.
- [Release notes](https://github.com/determinatesystems/magic-nix-cache-action/releases)
- [Commits](DeterminateSystems/magic-nix-cache-action@v2...v4)

---
updated-dependencies:
- dependency-name: DeterminateSystems/magic-nix-cache-action
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/application.yml

@@ -31,7 +31,7 @@ jobs:
     - name: Install Nix
       uses: DeterminateSystems/nix-installer-action@v10
     - name: Run the Magic Nix Cache
-      uses: DeterminateSystems/magic-nix-cache-action@v2
+      uses: DeterminateSystems/magic-nix-cache-action@v4
 
     - name: Check flake format
       run: nix develop --command nixpkgs-fmt --check flake.nix

.github/workflows/nixos.yml

@@ -27,7 +27,7 @@ jobs:
     - name: Install Nix
       uses: DeterminateSystems/nix-installer-action@v10
     - name: Run the Magic Nix Cache
-      uses: DeterminateSystems/magic-nix-cache-action@v2
+      uses: DeterminateSystems/magic-nix-cache-action@v4
 
     - name: Check Nix format
       run: |