Bump actions/checkout from 4 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v4...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>

Author: dependabot[bot]

.github/workflows/deploy-docs.yaml

@@ -20,7 +20,7 @@ jobs:
     steps:
       # https://github.com/actions/checkout
       - name: Checkout
-        uses: actions/checkout@v4.2.2
+        uses: actions/checkout@v6
         with:
           fetch-depth: 0  # otherwise, you will fail to push refs to dest repo
 

.github/workflows/main.yaml

@@ -26,7 +26,7 @@ jobs:
 
       # https://github.com/actions/checkout
       - name: Check out repository
-        uses: actions/checkout@v4.2.2
+        uses: actions/checkout@v6
         with:
           persist-credentials: false
 

.github/workflows/pypi-publish.yaml

@@ -13,7 +13,7 @@ jobs:
     permissions:
       id-token: write
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Install uv
         uses: astral-sh/setup-uv@v6