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/changelog.yml

@@ -15,7 +15,7 @@ jobs:
     timeout-minutes: 4
     if: "!contains(github.event.head_commit.message, 'update changelog')"
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Set up Ruby
         uses: ruby/setup-ruby@v1
         with:

.github/workflows/codeql-analysis.yml

@@ -24,7 +24,7 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       # Initialize the CodeQL tools for scanning.
       - name: Initialize CodeQL

.github/workflows/cpp.yml

@@ -21,7 +21,7 @@ jobs:
     runs-on: macos-latest
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: build
         run: |
           clang++ -std=c++2a --verbose -Wall -Wextra -pedantic -g \

.github/workflows/flawfinder.yml

@@ -28,7 +28,7 @@ jobs:
       security-events: write
     steps:
       - name: Checkout code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: flawfinder_scan
         uses: david-a-wheeler/[email protected]

.github/workflows/shellcheck-markdown.yml

@@ -20,7 +20,7 @@ jobs:
       run:
         shell: bash
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Run shellcheck
         run: |
           # test shell syntax of Markdown code snippets

.github/workflows/super-linter.yml

@@ -41,7 +41,7 @@ jobs:
       # Checkout the code base #
       ##########################
       - name: Checkout Code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           # linter requires full repository history
           fetch-depth: 0