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/gh-pages.yml

@@ -9,7 +9,7 @@ jobs:
   deploy:
     runs-on: ubuntu-22.04
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           submodules: true  # Fetch Hugo themes (true OR recursive)
           fetch-depth: 0    # Fetch all history for .GitInfo and .Lastmod

.github/workflows/htmltest.yml

@@ -7,7 +7,7 @@ jobs:
     name: Htmltest
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           submodules: true  # Fetch Hugo themes (true OR recursive)
           fetch-depth: 0    # Fetch all history for .GitInfo and .Lastmod

.github/workflows/metadata-docs.yml

@@ -52,7 +52,7 @@ jobs:
 
     steps:
       - name: Checkout pattern repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           path: ${{ env.PATTERN_DIR }}
 
@@ -75,7 +75,7 @@ jobs:
         working-directory: ${{ env.PATTERN_DIR }}
 
       - name: Checkout docs repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           path: ${{ env.DOCS_DIR }}
           repository: ${{ env.DOCS_REPO }}

.github/workflows/superlinter.yml

@@ -12,7 +12,7 @@ jobs:
 
     steps:
       - name: Checkout Code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           # Full git history is needed to get a proper list of changed files within `super-linter`
           fetch-depth: 0