Bump actions/checkout from 2 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v2...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]>

Author: dependabot[bot]

.github/workflows/check-bioc.yml

@@ -77,7 +77,7 @@ jobs:
       ## https://github.com/r-lib/actions/blob/master/examples/check-standard.yaml
       ## If they update their steps, we will also need to update ours.
       - name: Checkout Repository
-        uses: actions/checkout@v2
+        uses: actions/checkout@v6
 
       ## R is already included in the Bioconductor docker images
       - name: Setup R from r-lib