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/render-docs.yml

@@ -6,7 +6,7 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6
       with:
         fetch-depth: 0 # otherwise, there would be errors pushing refs to the destination repository.
     - name: Setup pandoc

.github/workflows/superlinter.yml

@@ -39,7 +39,7 @@ jobs:
       # Checkout the code base #
       ##########################
       - name: Checkout Code
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           # Full git history is needed to get a proper list of changed files within `super-linter`
           fetch-depth: 0