build(deps): bump DeterminateSystems/magic-nix-cache-action from 7 to 8

Bumps [DeterminateSystems/magic-nix-cache-action](https://github.com/determinatesystems/magic-nix-cache-action) from 7 to 8.
- [Release notes](https://github.com/determinatesystems/magic-nix-cache-action/releases)
- [Commits](DeterminateSystems/magic-nix-cache-action@v7...v8)

---
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]>

.github/workflows/build.yml

@@ -19,7 +19,7 @@ jobs:
       uses: actions/checkout@v4
     - name: Install Nix
       uses: DeterminateSystems/nix-installer-action@v14
-    - uses: DeterminateSystems/magic-nix-cache-action@v7
+    - uses: DeterminateSystems/magic-nix-cache-action@v8
     - name: Build some-pkgs
       run: nix run github:Mic92/nix-fast-build -- --skip-cached --no-nom --flake ".#packages.$(nix eval --raw --impure --expr builtins.currentSystem)"
   nix-flake-check:
@@ -33,6 +33,6 @@ jobs:
       uses: actions/checkout@v4
     - name: Install Nix
       uses: DeterminateSystems/nix-installer-action@v14
-    - uses: DeterminateSystems/magic-nix-cache-action@v7
+    - uses: DeterminateSystems/magic-nix-cache-action@v8
     - name: Build the checks
       run: nix run github:Mic92/nix-fast-build -- --skip-cached --no-nom --flake ".#checks.$(nix eval --raw --impure --expr builtins.currentSystem)"