Bump actions/checkout from 5 to 6 (#102)

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] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/publish_to_pypi.yml

@@ -9,7 +9,7 @@ jobs:
         runs-on: ubuntu-latest
         steps:
             - name: Checkout sources
-              uses: actions/checkout@v5
+              uses: actions/checkout@v6
 
             - name: Install uv
               uses: astral-sh/setup-uv@v7

.github/workflows/run_tests.yml

@@ -10,7 +10,7 @@ jobs:
       matrix:
         python-version: [3.9, 3.13]
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Install uv
         uses: astral-sh/setup-uv@v7
       - name: Set up Python ${{ matrix.python-version }}
@@ -30,7 +30,7 @@ jobs:
       matrix:
         python-version: [3.9, 3.13]
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Install uv
         uses: astral-sh/setup-uv@v7
       - name: Set up Python ${{ matrix.python-version }}