Bump DeterminateSystems/magic-nix-cache-action from 6 to 7

Bumps [DeterminateSystems/magic-nix-cache-action](https://github.com/determinatesystems/magic-nix-cache-action) from 6 to 7.
- [Release notes](https://github.com/determinatesystems/magic-nix-cache-action/releases)
- [Commits](DeterminateSystems/magic-nix-cache-action@v6...v7)

---
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/release.yml

@@ -45,7 +45,7 @@ jobs:
           authToken: ${{ secrets.CACHIX_AUTH_TOKEN }}
 
       - name: Configure Nix cache
-        uses: DeterminateSystems/magic-nix-cache-action@v6
+        uses: DeterminateSystems/magic-nix-cache-action@v7
         with:
           upstream-cache: https://trailofbits.cachix.org