⬆️ Bump actions/checkout from 4 to 5

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 5.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v4...v5)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '5'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/deploy-docs.yml

@@ -13,7 +13,7 @@ jobs:
   build-and-deploy:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v5
 
     - name: Install uv (and enable caching)
       uses: astral-sh/setup-uv@v6

.github/workflows/pytest.yml

@@ -10,7 +10,7 @@ jobs:
       CUDA: cpu       # or cu118, cu124, etc.
 
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v5
 
     - name: Install uv (and enable caching)
       uses: astral-sh/setup-uv@v6
@@ -59,7 +59,7 @@ jobs:
       CUDA: cpu
 
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v5
 
     - name: Download RDB7 forward barriers and geometries
       run: |