[github-action] bump actions/checkout from 5 to 6 (#20)

Bumps [actions/checkout](https://github.com/actions/checkout) from 5 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v5...v6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Iliyan Kostov <59366790+IliyanKostov9@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/flake-test.yml

@@ -10,7 +10,7 @@ jobs:
     name: Flake ❄️ Checker ✅
     runs-on: ubuntu-22.04
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0
       - uses: DeterminateSystems/nix-installer-action@v20
@@ -28,7 +28,7 @@ jobs:
     name: Flake ❄️ Lock 🔒️ Updater ✨
     runs-on: ubuntu-22.04
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0
       - uses: DeterminateSystems/nix-installer-action@v20

.github/workflows/jekyll-gh-pages.yaml

@@ -20,7 +20,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Setup Pages
         uses: actions/configure-pages@v5
       - name: Build with Jekyll

.github/workflows/security-scan.yaml

@@ -17,7 +17,7 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           fetch-depth: 0