⬆️ Bump actions/checkout from 5 to 6 (#817)

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>
Co-authored-by: Matt McKay <mmcky@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -19,7 +19,7 @@ jobs:
         os: [windows-latest, ubuntu-latest, macos-latest]
         python-version: [3.12, 3.13, 3.14]
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
       with:
         fetch-depth: 0
     - name: Cache conda
@@ -68,7 +68,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout source
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Set up Python
         uses: actions/setup-python@v6
         with:

.github/workflows/ci_np2.yml

@@ -12,7 +12,7 @@ jobs:
       max-parallel: 5
 
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - uses: conda-incubator/setup-miniconda@v3
       with:
         auto-update-conda: true