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] <[email protected]>

Author: dependabot[bot]

.github/workflows/check-code-with-shellcheck.yml

@@ -10,7 +10,7 @@ jobs:
     name: Github Actions
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - name: Run Shellcheck
       uses: ludeeus/action-shellcheck@master
       with:

.github/workflows/reviewdog.yml

@@ -11,7 +11,7 @@ jobs:
     name: Shellcheck testing
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: shellcheck
         uses: reviewdog/action-shellcheck@v1
         with:
@@ -25,7 +25,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: spelling or typos
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: misspell
         uses: reviewdog/action-misspell@v1
         with:

.github/workflows/update-copyright-year.yml

@@ -15,7 +15,7 @@ jobs:
       pull-requests: write
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Get current year
         id: year