ci: bump actions/checkout from 4 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v4...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>

Author: dependabot[bot]

.github/workflows/ci-lint.yml

@@ -22,7 +22,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           # Check out pull request's HEAD commit instead of the merge commit to
           # prevent gitlint from failing due to too long commit message titles,
@@ -67,7 +67,7 @@ jobs:
         # Always run this step so that all linting errors can be seen at once.
         if: always()
       - name: Ensure a clean code checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           clean: true
         if: always()

.github/workflows/ci-tests.yml

@@ -25,7 +25,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     steps:
       - name: Checkout code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Set up Go
         uses: actions/setup-go@v6
         with:

.github/workflows/docker-rofl-container-builder.yml

@@ -24,7 +24,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Determine tag name
         id: determine-tag

.github/workflows/release.yml

@@ -16,7 +16,7 @@ jobs:
       options: --user 1001
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           fetch-depth: 0
       - name: Set up Go