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](https://github.com/actions/checkout/compare/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>

.github/workflows/authors-file.yml

@@ -10,7 +10,7 @@ jobs:
 
     steps:
       - name: Checkout HEAD
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           fetch-depth: 0
 

.github/workflows/linux.yml

@@ -64,7 +64,7 @@ jobs:
 
     steps:
       - name: Checkout HEAD
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Turn on Problem Matcher
         run: echo "::add-matcher::.github/problem-matchers/gcc.json"

.github/workflows/windows.yml

@@ -29,7 +29,7 @@ jobs:
 
     steps:
       - name: Checkout HEAD
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           fetch-depth: 0