Bump actions/checkout from 3 to 6 (#90)

Bumps [actions/checkout](https://github.com/actions/checkout) from 3 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v3...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]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/cpp.yml

@@ -16,7 +16,7 @@ jobs:
       matrix:
         os: [ubuntu-24.04, ubuntu-22.04, windows-2022, macos-14, macos-15]
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v6
       - name: Setup cmake
         uses: jwlawson/[email protected]
         with:
@@ -38,7 +38,7 @@ jobs:
         os: [ubuntu-22.04, ubuntu-24.04]
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v6
       - name: Cache dependencies
         uses: actions/cache@v4
         with:

.github/workflows/pre-commit.yml

@@ -11,7 +11,7 @@ jobs:
     name: Pre-commit checks
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v6
       - uses: actions/setup-python@v4
         with:
           python-version: "3.10"

.github/workflows/pypi.yml

@@ -12,7 +12,7 @@ jobs:
     name: Build source distribution
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v6
 
       - name: Build sdist
         run: pipx run build --sdist ${{github.workspace}}/python/
@@ -31,7 +31,7 @@ jobs:
         os: [ubuntu-24.04, windows-2022, macos-15]
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v6
 
       - name: Build test wheels (only PRs)
         if: github.event_name != 'release'

.github/workflows/python.yml

@@ -13,7 +13,7 @@ jobs:
         os: [ubuntu-24.04, ubuntu-22.04, windows-2022, macos-14, macos-15]
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v6
       - name: Set up Python3
         uses: actions/setup-python@v3
         with: