build(deps): Bump DeterminateSystems/magic-nix-cache-action from 4 to 6

Bumps [DeterminateSystems/magic-nix-cache-action](https://github.com/determinatesystems/magic-nix-cache-action) from 4 to 6.
- [Release notes](https://github.com/determinatesystems/magic-nix-cache-action/releases)
- [Commits](DeterminateSystems/magic-nix-cache-action@v4...v6)

---
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/check.yml

@@ -12,7 +12,7 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - uses: DeterminateSystems/nix-installer-action@v10
-      - uses: DeterminateSystems/magic-nix-cache-action@v4
+      - uses: DeterminateSystems/magic-nix-cache-action@v6
       - uses: DeterminateSystems/flake-checker-action@v5
 
       - name: Check nix file formatting ❄️

.github/workflows/gh-pages.yml

@@ -16,7 +16,7 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - uses: DeterminateSystems/nix-installer-action@v10
-      - uses: DeterminateSystems/magic-nix-cache-action@v4
+      - uses: DeterminateSystems/magic-nix-cache-action@v6
 
       - run: |
           nix build . -L

.github/workflows/gist.yml

@@ -12,7 +12,7 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - uses: DeterminateSystems/nix-installer-action@v10
-      - uses: DeterminateSystems/magic-nix-cache-action@v4
+      - uses: DeterminateSystems/magic-nix-cache-action@v6
 
       - run: |
           nix build .#fmt-as-json && ./result