ci: bump DeterminateSystems/update-flake-lock from 27 to 28

Bumps [DeterminateSystems/update-flake-lock](https://github.com/determinatesystems/update-flake-lock) from 27 to 28.
- [Release notes](https://github.com/determinatesystems/update-flake-lock/releases)
- [Commits](https://github.com/determinatesystems/update-flake-lock/compare/v27...v28)

---
updated-dependencies:
- dependency-name: DeterminateSystems/update-flake-lock
  dependency-version: '28'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

.github/workflows/ci.yml

@@ -8,7 +8,7 @@ jobs:
   ci:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: cachix/install-nix-action@v31
         with:
           nix_path: nixpkgs=channel:nixos-unstable

.github/workflows/clear-cache.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Clear cache
-        uses: actions/github-script@v7
+        uses: actions/github-script@v8
         with:
           script: |
             console.log("About to clear")

.github/workflows/update-flake.yml

@@ -10,11 +10,11 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Install Nix
         uses: cachix/install-nix-action@v31
       - name: Update flake.lock
-        uses: DeterminateSystems/update-flake-lock@v27
+        uses: DeterminateSystems/update-flake-lock@v28
         with:
           token: ${{ secrets.GH_TOKEN_FOR_UPDATES }}
           pr-labels: |