build(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] <[email protected]>

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -15,7 +15,7 @@ jobs:
 
     steps:
 
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - name: Install clang-tidy
       run: |
         sudo apt-get install -y clang-tidy
@@ -101,7 +101,7 @@ jobs:
        CXXFLAGS: '${{ matrix.san_cflags }} ${{ matrix.asan_cflags }}'
 
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - name: Build and test
       run: |
          cmake \
@@ -125,7 +125,7 @@ jobs:
             cmake_shared: 'NO'
 
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - uses: ilammy/msvc-dev-cmd@v1
     - name: Build and test
       run: |