Bump actions/checkout from 5 to 6 (#478)

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]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Andrei Paleyes <[email protected]>

Author: dependabot[bot]

.github/workflows/codecov.yml

@@ -13,7 +13,7 @@ jobs:
 
     steps:
 
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - name: Set up Python 3.10
         uses: actions/setup-python@v6

.github/workflows/format.yml

@@ -10,7 +10,7 @@ jobs:
   check_format:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - name: Set up Python 3.10
       uses: actions/setup-python@v6
       with:

.github/workflows/tests.yml

@@ -15,7 +15,7 @@ jobs:
         python-version: ["3.10", "3.13"]
 
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - name: Set up Python ${{ matrix.python-version }}
       uses: actions/setup-python@v6
       with:
@@ -68,7 +68,7 @@ jobs:
     runs-on: ${{ matrix.os }}
 
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - name: Set up Python 3.10
       uses: actions/setup-python@v6
       with: