chore(deps): bump actions/checkout from 5 to 6

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>

Author: dependabot[bot]

.github/workflows/lint.yml

@@ -13,7 +13,7 @@ jobs:
   shellcheck:
     runs-on: ubuntu-24.04
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: ShellCheck all run.sh / cleanup.sh
         run: |
           set -e
@@ -30,15 +30,15 @@ jobs:
   yamllint:
     runs-on: ubuntu-24.04
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: ibiqlik/action-yamllint@v3
         with:
           config_file: .yamllint.yml
 
   markdownlint:
     runs-on: ubuntu-24.04
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: DavidAnson/markdownlint-cli2-action@v20
         with:
           globs: |
@@ -48,7 +48,7 @@ jobs:
   kubectl-dry-run:
     runs-on: ubuntu-24.04
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Install kubectl
         uses: azure/setup-kubectl@v4
       - name: kubectl --dry-run=client on every manifest