build(deps): bump DeterminateSystems/magic-nix-cache-action

Bumps [DeterminateSystems/magic-nix-cache-action](https://github.com/determinatesystems/magic-nix-cache-action) from 1828eb4e5414b8dfe36daae53ea3e4b8c3fdec7a to b4a9864e3a8ab8179be30f2e70fd71fe9996bb9d.
- [Release notes](https://github.com/determinatesystems/magic-nix-cache-action/releases)
- [Commits](DeterminateSystems/magic-nix-cache-action@1828eb4...b4a9864)

---
updated-dependencies:
- dependency-name: DeterminateSystems/magic-nix-cache-action
  dependency-version: b4a9864e3a8ab8179be30f2e70fd71fe9996bb9d
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/checks.yml

@@ -14,7 +14,7 @@ jobs:
       with:
         persist-credentials: false
     - uses: DeterminateSystems/nix-installer-action@b66b36319cc6fde4ea85edd583b088c65d6b8710 # main
-    - uses: DeterminateSystems/magic-nix-cache-action@1828eb4e5414b8dfe36daae53ea3e4b8c3fdec7a # main
+    - uses: DeterminateSystems/magic-nix-cache-action@b4a9864e3a8ab8179be30f2e70fd71fe9996bb9d # main
     - uses: DeterminateSystems/flake-checker-action@fd11c504211041399e78bd1027d885160c8ae4c2 # main
     - run: nix flake check -L