Bump DeterminateSystems/magic-nix-cache-action from 2 to 3

Bumps [DeterminateSystems/magic-nix-cache-action](https://github.com/determinatesystems/magic-nix-cache-action) from 2 to 3.
- [Release notes](https://github.com/determinatesystems/magic-nix-cache-action/releases)
- [Commits](DeterminateSystems/magic-nix-cache-action@v2...v3)

---
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]>

Author: dependabot[bot]

.github/workflows/nix.yml

@@ -15,7 +15,7 @@ jobs:
     - name: Install Nix
       uses: DeterminateSystems/nix-installer-action@v9
     - name: Run the Magic Nix Cache
-      uses: DeterminateSystems/magic-nix-cache-action@v2
+      uses: DeterminateSystems/magic-nix-cache-action@v3
 
     - name: Build the default flake output
       run: nix build